Progress in Olefin Polymerization Catalysts and Polyolefin Materials: Proceedings of the First Asian Polyolefin Workshop, Nara, Japan, December

Studies in Surface Science and Catalysis 161 CATALYSTS PROGRESS IN OLEFIN POLYMERIZATION CATALYSTS MATERIALS AND POLYO...

Author: Takeshi Shiono | Kotohiro Nomura | Minoru Terano

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Studies in Surface Science and Catalysis 161

CATALYSTS PROGRESS IN OLEFIN POLYMERIZATION CATALYSTS MATERIALS AND POLYOLEFIN MATERIALS

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Studies in Surface Science and Catalysis and J.T. J.T. Yates Advisory Editors: B. Delmon and Series Editor: G. G. Centi

Vol. 161

IN OLEFIN PROGRESS IN CATALYSTS POLYMERIZATION CATALYSTS MATERIALS AND POLYOLEFIN MATERIALS Poiyoiefin Workshop, Nara, Japan, Proceedings of the First Asian Polyolefin December 7-9, 2005

Edited by Takeshi Shiono Graduate School of of Engineering, Hiroshima University Graduate Higashi-Hiroshima, Japan

Nomura Kotohiro Nomura of Science and and Technology Nara Institute of Nara, Japan Minoru Terano of Science and and Technology Japan Advanced Institute of Ishikawa, Japan

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Committee

Academic Lee, Dong-Ho (Kyunpook National University, Korea) Li, Bo-Geng (Zhejiang University, PR China) Noh, Seok Kyun (Yeungnam University, Korea) Nomura, Kotohiro (Chair, NAIST, Japan, General Secretary) Shiono, Takeshi (Chair, Hiroshima University, Japan) Sun, Wen-Hua (Institute of Chemistry, CAS, PR China) Terano, Minoru (Chair, JAIST, Japan) Woo, Seong Ihl (KAIST, Korea) Industry Aral, Toru (Denka Co.) Hujita, Takashi (Toho Catalyst Co., Ltd.) Imuta, Jun-iehi (Mitsui Chemicals Inc.) Kuramoto, Masahiko (Idemitsu Kosan Co., Ltd.) Miyatake, Tatsuya (Sumitomo Chemical Co., Ltd.) Takahashi, Mitsuru (Tosoh Fineehem. Corp.) Tayano, Takao (Japan Polypropylene Corp.) Watanabe, Harumi (Asahi Kasei Chemicals Corp.) Organized by Catalysis Society of Japan, Polymerization Catalysis Division Coorganized by The Chemical Society of Japan The Japan Petroleum Institute The Society of Polymer Science, Japan Nara Convention Bureau

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Contents Committee

v

Preface

1

xv

Creation of New Polyolefm Hybrids on the Surface of Molded Polypropylene Sheet S. Matsuo, T. Matsugi, J. Saito, N. Kawahara, H. Kaneko, N. Kashiwa (R&D Center, Mitsui Chemicals, Inc., Japan)

1

2

Japanese National Project for the Innovation of Industrial Polypropylene Process Technology 7 M. Terano", K. Suehiroh, T, Sagae", E. Tobitad ("Japan Advanced Institute of Science & Technology,l'Mitsui Chemicals, Inc., "Japan Polypropylene, Co., Asahi Denka Co., Ltd., Japan)

3

Novel Energy and Cost Saving Polypropylene Stabilization via addition of Antioxidant into Polymerization System H. Yokotaa, K. Nomura", T. Horikoshi3, Y. Negishia, N. Kawamoto11, E. Tobitaa, M. Teranob ("Asahi Denka Co., Ltd., Japan Polypropylene, Co., Japan)

4

5

Polymerization Behavior with Metallocene Catalyst Supported by Clay Mineral Activator H. Nakano, T, Takahashi, H. Uehino, T, Tayano, T. Sugano (Polymerization Technical Center, Japan Polypropylene Corporation, Japan) Regulating the Structure of Ethylene-Propylene Copolymer for Polyolefin In-reactor Alloy with Improved Properties Q. Dong, N. Li, X. Wang, Z. Fu, J. Xu, Z. Fan (The Institute ofPolymer Science, Zhejiang University, China) VII

13

19

25

viii 6

7

8

9

Contents Application of High Resolution FTIR Spectroscopy in Structural Characterization of Polyethylene and Ethylene Copolymers Z. Sua, X. Zhanga, N. Kanga, Y. Xub, Y. Zhao", D. Wang,"" J. Wub, D. Xua ("State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, China) Microstructure Characterization of Polyolefins. TREF and CRYSTAF B. Monrabal (Polymer Char, Spain) Ultra-high Molecular Weight Polyethylene from Slurry INSITE™ Technology Koichi Hasebe, Akio Fujiwara, Takashi Nozaki, Koichi Miyamoto, and Harumi Watanabe {Polyolefins Development Dept, Polyethylene Division, Asahi Kasei Chemicals Corporation, Japan) Effects of Solvents in Living Polymerization of Propene with ^BuNSiMe2(3,6-^Bu2Flu)]TiMerMMAO Catalyst T. Shiono, Z. Cai, Y. Nakayama (Graduate School of Engineering, Hiroshima University, Japan)

10 Preparation of Ethylene/Polyhedral Oligomeric Silsesquioxane(POSS) Copolymers with rae-Et(Ind)2ZrCl2/MMAO Catalyst System D.-H Leea, K.-B. Yoona, M.-S. Junga, J.-K. Sungb, S. K. Nohc ("Department of Polymer Science, Kyungpook National University, Korea, b R&D Center, Korea Petrochemical Inc., Korea, cSchool of Chemical Engineering and Technology, Yeongnam University, Korea) 11 Norbomene and Ethylene Polymerization with Palladium and Nickel Complexes with Potentially Tri- or Tetradentate Ligands D. W. Leea, C. Kimb, I.-M. Leea ("Department of Chemistry, Inha University, Korea, ^Department of Fine Chemistry, Seoul National University of Technology, Korea) 12 Effects of Bridge Nature of Dinuclear Half-Titanocenes on Polymerization Properties Seok Kyun Noh\ Yong Rok Lee\ Won Seok Lyoob, Dong-Ho Leec ("School of Chemical Engineering and Technology, Yeungnam University, Korea, School of Textiles, Yeungnam University, Korea, ^'Department of Polymer Science, Kyungpook National University, Korea)

31

35

43

47

53

59

69

Contents

ix

13 Modification of Catalytic Properties of Homogeneous Metallocene Catalytic Systems in Propylene Polymerization under Action of Triisobutylaluminum and Lewis Bases 77 N.M. Bravaya, E.E. FalngoPd, EA. Sanginov, A.N. Panin, O.N. Babkina, S.L. Saratovskikh, O,N, Chukanova, A.G. Ryabenko, E.N. Ushakov {Institute of Problems of Chemical Physics, Russian Academy ofSciences, Russia) 14 Iron(II) Complexes Ligated with 2-Irnino-l,10-Phenanthroline for Ethylene Activation W.-H. Sun, S. Jie, S. Zhang, W. Zhang (Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, China)

87

15 Polymerization of 1 -Hexene and Copolymerization of Ethylene with 1-Hexene Catalyzed by Cationic Half-Sandwich Scandium Alkyls 95 Y. Luob, Z. Houa (fl Organometallic Chemistry Laboratory, RIKEN, Japan, b PRESTO, Japan Science and Technology Agency, Japan) 16 Stereoerrors Formation in the Polymerization of Deuterated Propylene 105 V. Volkis, A. Lisovskii, M, S. Eisen (Department of Chemistry and Institute of Catalysis Science and Technology, Technion Israel Institute of Technology, Israel) 17 Vinylic Polymerization of Norbornene with Neutral Nickel(IT) Complexes Bearing P-Diketiminato Chelate Ligands 113 Y.-Q. Duan, X.-F. Li, Y.-S. Li (State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, China, and Graduate School of the Chinese Academy ofSciences) 18 Effect of Anionic Ancillary Ligand in Ethylene Polymerization Catalyzed by (Arylimido)vanadium Complexes Containing Aryloxide, Ketimide Ligand 123 K. Nomura, W. Wang, J. Yamada (Graduate School of Materials Science, Mara Institute of Science and Technology, Japan) 19 Computational Approach on the Interaction between CrO3 and Ethylene as a Model for the Understanding of Phillips Catalyst 129 B. Liu, W. Xia, M. Terano (School of Materials Science, Japan Advanced Institute of Science and Technology, Japan)

x

Contents

20 Olefin Polymerization by Bimetallic Zr Catalyst. Ligand Effect for Activity and Stereoselectivity 135 J. Kuwabara, D. Takeuehl, K. Osakada (Chemical Resources Laboratory, Tokyo Institute of Technology, Japan) 21 Synthesis, Characterization and Ethylene Reactivity of 2-Ester-6-iminapyridyl Metal Complexes W, Zhang, B. Wu, W.-H. Sun (Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, China)

141

22 Ligand Effect in Syndiospecific Styrene Polymerization and Ethylene/Styrene Copolymerization by Some Nonbridged Half-Titanoeenes Containing Anionic Donor Ligands H. Zhang, K. Nomura (Graduate School of Materials Science, Nara Institute of Science and Technology, Japan)

147

23 Titanium and Zirconium Complexes Bearing a Trialkoxoamine Ligand: Synthesis and Olefin Polymerization Activity 153 P, Sudhakar, G. Sundararajan (Department of Chemistry, Indian Institute of Technology, India) 24 Stereoselective Polymerization of Styrene by FI Catalysts 159 K. Michiue8, M. Ondab, M. Mitanf, T. Fujita a f5 & D Center, Mitsui Chemicals, Inc., Japan, Mitsui Chemical Analysis & Consulting Service, Inc., Japan) 25 Synthesis of Bis(imino)pyridine Complexes of Group 5 Metals and Their Catalysis for Polymerization of Ethylene and Norbornene Y, Nakayama, N. Maeda, T. Shiono (Graduate School of Engineering, Hiroshima University, Japan) 26 Ethylene Polymerization with an Anilinonaphthoquinone-Ligated Nickel Complex M. Okada, Y. Nakayama, T. Shiono (Graduate School of Engineering, Hiroshima University, Japan) 27 Ring Opening Metathesis Polymerization of Norbornene Catalyzed by V(CH2SiMe3)a(N-2,6-Me2C6H3XN=C'Bu). In Situ Generation of the Vanadium-Alkylidene K. Nomura, J, Yamada (Graduate School of Materials Science, Nara Institute of Science and Technology, Japan)

165

171

175

Contents 28 Ethylene/2-Methyl-1 -Pentene Copolymerization Catalyzed by Half-Titanocenes Containing Aryloxo Ligand: Effect of Cyclopentadienyl Fragment K. Nomura, K. Itagaki (Graduate School of Materials Science, Nora Institute of Science and Technology, Japan) 29 Synthesis and Optical Properties of Cyeloolefm Copolymers K.-B. Yoon", H. Y. Lee8, S. K. Nohb, D.-H Leea {"Department ofPolymer Science, Kyungpook National University, Korea, bSchool of Chemical Engineering and Technology, Yeongnam University, Korea) 30 Effects of Temperature in Syndiospecific Living Polymerization of Propylene with [r-BuNSiMe2(3,6-f-Bu2Flu)]TiMe2-MMAO Catalyst Z. Cai, Y, Nakayama, T, SHono (Graduate School ofEngineering, Hiroshima University, Japan) 31 Copolymerization of Styrene Derivatives and Cycloolefin with Ni Compound/MAO Catalyst N. Nishimura, K. Maeyama, A. Toyota (Graduate School ofEngineering, Tokyo University of Agriculture and Technology, Japan)

xi

179

185

189

193

32 Additive Effects of Dialkylaluminum Hydrides on Propylene-1,3-Butadiene Copolymerization Using an Isospecific Zirconocene Catalyst 197 T. Ishihara", H. T. Bana, H. Hagihara\ T, Shionoe ("Japan Chemical Innovation Institute, Japan, * National Institute of Advanced Industrial Science and Technology, Japan,c Graduate School of Engineering, Japan) 33 Pd Complex-Promoted Cyclopolymerization ofDiallylmalonates 201 S. Park, D. Takeuchi, K. Osakada (Chemical Resources Laboratory, Tokyo Institute of Technology, Japan) 34 Synthesis of Polymeric Radical Scavengers via ROMP of Norbomene Derivatives and Their Antioxidation Activities K. Horikawa, K. Maeyama, A, Toyota (Graduate School ofEngineering, Tokyo University of Agriculture and Technology, Japan)

205

35 Vinyl Polymerization of Norbomene over Supported Nickel Catalyst 209 J. Hou, W. Zhang, S. Jie, W.-H. Sun (Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, China)

xii

Contents

36 Effect of Catalyst Loading in Olefin Polymerization Catalyzed by Supported Half-Titanoeenes on Polystyrene through Phenoxy Linkage

213

B. Kitiyanan, K. Nomura {Graduate School of Materials Science, Nara Institute of Science and Technology, Japan) 37

38

39

Theoretical Study on Active Site Formation of Olefin Metathesis and Olefin Polymerization in Phillips CrOx/SiO 2 Catalyst by PIO Analysis A. Shigaa, B. Liub, M. Teranob f LUMMOX Research Lab., Japan, h School of Materials Science, Japan Advanced Institute of Science and Technology, Japan)

219

Plausible Mechanism for the Formation and Transformation of Active Sites on Novel Phillips Type Catalyst with New Organo-siloxane Ligand W. Xia, B. Liu, Y. Fang, D. Zhou, M. Terano (School of Materials Science, Japan Advanced Institute of Science and Technology, Japan)

225

Influence of Polymer Morphology on Photo-stability of Polypropylene/SiO2 Nanocomposites K. Suminoa, K. Asukaa, B. Liua, M. Yamaguchf, M. Terano8, T. Kawamurab, K. Nittaa (a School of Materials Science, Japan Advanced Institute of Science and Technology, Japan, * Graduate School of Natural Science and Technology, Kanazawa University, Japan)

40

Photo-oxidation of Polyolefln/Clay Composites S. Zhang, H, Qin, M. Yang (Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, P. R. China)

41

Effects of Silica Particles on the Transparency of Polypropylene Based Nanocomposites Kazuo Asukaa, Iku Kouzaf, Boping Liua, Minoru Teranoa, Koh-hei Nfttab ("School of Materials Science, JAISTJapan, hGraduate School of Natural Sci and Tech., Kanazawa University, Kakvma, Kanazawa, 920-1192, Japan)

42

Propene Polymerization by a/wa-Fluorenylamidodimethyltitanium Activated with SiO2-Supported Modified Methylalrninoxane Takeshi Shiono3*, Takashi Matsumaeb, Kef Nishiib, Tomiki Ikedab ("Graduate School of Engineering, Hiroshima University, Chemical Resources Laboratory, Japan)

229

233

237

241

Contents 43 Branched-PE/i-PP Reactor Blends Prepared through Ethylene Gas-Phase Polymerization Catalyzed by a-Diimine Nickel Supported on iPP Particles Chtmwen Giro", Hong Fan*, Bo-Geng Li", Shiping Zhub ("State Key Laboratory of Polymer Reaction Engineering, Department of Chemical and Biochemical Engineering, Zhejiang University, China, Department of Chemical Engineering, McMaster University, Canada)

44 Kinetics of Propylene Bulk Polymerization with a Spherical Ziegler-Natta Catalyst Bogeng L i", Hong Fan a, Jijiang Htta, Shiping Zhub ("State Key Laboratory of Polymer Reaction Engineering, Department of Chemical and Biochemical Engineering, Zhejiang University, China, bDepartment of Chemical Engineering, McMaster University, Canada) 45

Effect of a-Olefins on Copolymerization of Ethylene and a-Olefin with [t-BuNSiMe 2 Flu]TiMe 2 Catalyst $ Nawaporn Intaragamjona, Takeshi Shionob*, Bunjerd Jongsomjit""* Piyasan Praserthdam3* ("Center of Excellence on Catalysis and Catalytic Reaction Engineering, Department of Chemical Engineering, Faculty of Engineering Chulalonngkorn University, Thailand,bDepartment of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Japan)

xili

245

253

271

Author Index

275

Subject Index

279

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Preface

More than a half-century has passed since the finding of Ziegler-Natta catalysts and a quarter-century from that of metallocene catalysts. The development of sophisticated production systems owing to the innovative catalyst technology has made polyolefm one of the most important polymer materials. Considerable research effort has been continuously paid on polyolefin technology in the world, and Asia has been growing up as one of the most active regions in this field. Asian Polyolefin Workshop (APO) was thus planned to provide a venue for Asian scientists and engineers identifying and exploring the areas of common interests. The 1 st APO was held in Nara on December 7th - 9th, 2005, with more than 100 participants from China, Israel, India, Japan, Korea, Russia, Spain and Thailand. The workshop concerned the following research topics with 34 oral and 37 poster presentations; 1) Heterogeneous olefin polymerization catalysts Traditional Ziegler-Natta, Phillips, heterogenized metallocene and post metallocenes 2) Homogeneous olefin polymerization catalysts Traditional Ziegler-Natta, metallocene and post metallocenes 3) Precise synthesis of new polyolefins 4) Structure and properties of polyolefins 5) Engineering aspects of olefin polymerization This book is a collection of the important papers presented at the Workshop, We believe that these works will stimulate further research as well as contribute to an understanding of the activity of Asia in this field. April, 2006 Takeshi Shiono Kotohiro Nomura Minoru Terano Editors xv

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Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

1

Creation of New Polyolefin Hybrids on the Surface of Molded Polypropylene Sheet Shingo Matsuo*, Tomoaki Matsugi, Junji Saito, Nobuo Kawahara, Hideyuki Kaneko, Norio Kashiwa R&D Center, Mitsui Chemicals, Inc., 580-32, Nagaura Sodegaura, Chiba, 299-0265, Japan

Abstract Surface polymerization of 2-hydroxyethyl methacrylate (HEMA) at the initiation sites on the molded sheet of polypropylene macroinitiator (PP-MI) was performed by a CuBr mediated controlled radical polymerization (CRP). The obtained sheet was coated with poly(HEMA), then analyzed by attenuated total reflection infrared (ATR/1R) and transmission electron microscopy (TEM) to investigate the structure and the morphology. It was revealed that PP-graft-poly(HEMA) was successfully synthesized on the sheet and showed unique morphological features. 1. INTRODUCTION Polyolefins (POs) are the most widely used commercial polymers. On the other hand, it is becoming important to add new functions into POs in order to broaden the applications vis-a-vis certain highly valuable fields. One approach to develop this point that has been attracting much attention is the creation of hybrid materials having chemical linkage between PO and non-PO [1]. In order to produce these materials, it is necessary to apply either PO macroinitiator [2,3,4], PO maeromonomer [5,6] or reactive PO [7]. By doing so, it is possible to create a new class of PO/non-PO hybrid polymers possessing unique topologies, compositions and properties. Recently, some methods have been developed for introduction of functional groups into PO, for example, eopolymerization of olefin and polar monomers [2,8,9]. This functional PO was useful to create PO macroinitiator for controlled radical polymerization (CRP). It has already been reported in our

1

S, Matsuo et al.

previous paper [3] that the method to produce polyethylene-block-poly(methyl methacrylate) block copolymers under solution conditions is by using terminally esterified polyethylene as a PO macroinitiator. But to produce POblock or graft-non-PO copolymers like that on molded sheet has not yet been reported. In this paper, we would like to report the CRP of 2-hydroxyethyl methacrylate (HEMA) to prepare PP-graft-poly(HEMA) on a molded sheet of PP-MI by using PO macroinitiator techniques and the results of surface observations. 2. EXPERIMENTAL Typical example for synthesis of polypropylene macroinitiator (PP-MI) Toluene (1 500 mL) was introduced into 2 000-mL glass flask equipped with a mechanical stirrer, a condenser, and a thermometer under nitrogen. After the solvent was thermostated to 40°C, then propylene gas was fed (100 L/h) for 20 min, triisobutylaluminium (44 mmol) and 10-undecen-l-ol (40 mmol) were added to the reactor. Pretreated solution of rac-ethylenebis(indenyl)zirconium dichloride (Et(Ind)2ZrCl2, 0.020 mmol) and methylaluminoxane (MAO, 4.0 mmol) in 10 ml toluene for 5 min was added to start polymerization. The polymerization was conducted for 20 min under vigorous stirring (600 rpm). Isobutyl alcohol (10 mL) was added to terminate the polymerization. The resulting solution was poured into methanol (3 000 mL) with concentrated HCl (5 mL) to precipitate the copolymer. The resulting polymer was collected by filtration, washed with methanol (300 mL x3), and dried under vacuum. Thus 53.6 g of isotactic poly(propylene-eo- 10-undecen-l-ol) was obtained as white powder (Mn: 15 400). lR NMR analysis revealed that 1.0 mol% of 10-undecenl-ol was incorporated into the copolymer. The resulting poly(propylene-eo- 10-undecen-l-ol) (50 g, 12 mmol of OH group), triethylamine (72 mmol), 2-bromoisobutyryl bromide (60 mmol), and hexane (600 mL) were added to a 1 000 mL-glass flask equipped with a mechanical stirrer, a condenser, and a thermometer under nitrogen. The mixture was heated to 80 °C and stirred for 80 min. Then, the reaction mixture was cooled to room temperature. The precipitated polymer was collected by filtration, washed with methanol, IN HCl (aq), and dried at 50 °C under vacuum. Thus, esterified PP as a macroinitiator was obtained in quantitative yield. Typical example for controlled radical polymerization (CRP) on the surface of PP-MI sheet A typical CRP was performed as follows, A PP-MI sheet (ca. 1 mm of thickness) prepared by hot-pressing method at 180 °C (10 Mpa, 1 min) was set into 500-mL flat-bottomed glass flask equipped with a

1, Creation of New Polyolefin Hybrids on the Surface of Molded Polypropylene Sheet 3

magnetic stirrer. Dried ethanol (250 mL) and 2-hydroxyethyl methacrylate (HEMA, 50 mL) were added to the flask under nitrogen atmosphere and stirred for 20 min at 25 °C. Ethanol and HEMA were degassed by bubbling with nitrogen for 30 min prior to use. CuBr (5,3 mmol) and N,N,N',N",N"pentamethyldiethylenetriamine (PMDETA, 10.6 mmol) were dissolved in ethanol (5 mL) and stirred for 5 min, then the solution was added into the flask to initiate the polymerization. The polymerization was conducted with stirring at 25 °C. After the desired polymerization time, the polymerization was stopped, and the resulting sheet was washed in excess methanol. The sheet was dried at 80 °C under vacuum. 3. RESULTS AND DISCUSSION 3.1. Preparation of polypropylene macroinitiator A synthetic route for preparation of polypropylene macroinitiator (PPMI) is shown in Scheme 1. Hydroxylated PP was prepared by copolymerization of propylene and 10-undecen-l-ol with Etflnd^ZrCla/MAO at 40 °C. Triisobutylaluminium was used as a reagent for masking hydroxyl group of 10undecen-l-ol. The resulting polymer solution was treated with acidic methanol to remove catalyst residues and aluminum moiety which caused gel formation. The thus obtained hydroxylated PP was treated with 2-bromoisobutyrylbromide and triethylamine in hexane at 80 °C to produce esterified PP, which was able to work as a macroinitiator (i.e. PP-MI) for CRP. This PP-M1 was molded by hotpressing (ca. 1 mm of thickness) at 180 °C, Scheme 1. Preparation of PP Macroinitiator C'BukAl

n AI /Q

Toluene

»

Propylene Metallocene/ MAO

MeOH

Toluene/4CTC O B r

-^

B r

/Et 3 N

Hexane OH

OH

n

= PP Macroinitiator (PP-MI)

4

S, Matsuo et al,

3.2. Controlled radical polymerization on the surface o/PP sheet The presence of initiation sites exposed on the surface was confirmed by attenuated total reflection infrared (ATR/IR) analysis. CRP of HEMA on the surface of PP-MI sheet was conducted at 25 °C in ethanol for 24 h. The surface of the sheet was obviously changed to rough and opaque after CRP, then it was analyzed by ATR/IR and transmission electron microscope (TEM) in detail. Polymerization Time Oh (PP-MI) Ester G=O of Foly(HEMA) |

3h

9h

24h vO-H

vC-H

vC=O(1?30) 4000

3B0D 3200

2800 2400 2000 1800 1200 800 WavenumberCerrr1)

400

Figure 1. ATR/IR spectra on the surface of PP-MI sheet

4000 3MD 3200 2800 2400 2000 1600 1200 BOO 400 Wavenumbers (em )

Figure 2. ATR/IR spectrum on the surface of homo PP sheet after treated under the same conditions as CRP

Figure 1 shows the change of ATR/IR spectra on the surface of the sheet. As the polymerization advanced, the absorption of the hydroxyl group and the carbonyl group derived from the poly(HEMA) became stronger with

1, Creation of New Polyolefin Hybrids on the Surface of Molded Polypropylene Sheet 5

lowering that of the alkyl group of the PP main chain. Meanwhile, the same absorption of the hydroxyl group and the carbonyl group was not observed on the surface of the commercially available homo PP sheet treated under the same conditions as the control (Figure 2). These results suggest that poly(HEMA) was propagated from the initiation sites on the sheet like the image in Figure 3. initiating site

Surface of PP-MI press-sheet Figure 3. Image of CRP on the surface of PP-MI press sheet

Moreover, Figure 4 showed the spectra of the cross section of the sheet after 24h polymerization in 2 um depth at each point (a-c). There was little absorption derived from the hydroxyl group and smaller absorption derived from the carbonyl group on the inside of the sheet (c), compared to the surface (a). These data also confirmed that the CRP of HEMA successfully occurred on the surface of the sheet. C u t t i n g bv tbc d i a m o n d knife

4000

3SO0

3200

2SO0 £400 2000 VVavenumbeitcnr 1 )

1600

1200

800

Figure 4. ATR/IR spectra, of the cross section of PP-graft-poly(HEMA) sheet

S. Matsuo et al.

(a)

Poly(HEMA)

(b)

PP-MI phase Figure 5. TEM image of the section nearby the surface of PP-graft-poly(HEMA) sheet at a magnification of (a) x 5 000 and (b) x 60 000

Furthermore, TEM observation was also examined in order to observe the change of the morphology of the surface on the sheet. Figure 5 shows the TEM images of the surface section of the same sheet in Figure 4. The thickness of the poly(HEMA) layer was in the range of about 5-20 um. The interface between PP and poly(HEMA) phase was not clear in the magnified image (b), probably derived from the chemical linkage. These TEM images support the results of ATR/IR in Figure 4 well. 4. Conclusions PP-graft-poly(HEMA) hybrid polymer on the surface of PP was successfully produced by the combination of metallocene catalyzed olefin polymerization followed by CRP. This technique should be applied to introduce polar polymer segments onto the surface of the various molded parts based on POs. Another kind of PO hybrid modified on the surface is now under investigating and will be reported soon. References [1] For recent review: T.C. Chung, Prog. Polym. Sci. 27 (2002) 39-85. [2] N. Kashiwa, T. Matsugi, S. Kojoh, H. Kaneko, "N. Kawahara, S. Matsuo, T. Nobori, J. Imuta, J. Polym. Sci. Part A: Polym. Chem. 41 (2003) 3657-3666. [3] T. Matsugi, S. Kojoh, N. Kawahara, S. Matsuo, H. Kaneko, N. Kashiwa, J. Polym. Sci. Part A: Polym. Chem. 41 (2003) 3965-3973. [4] Y. Inoue, T. Matsugi, N. Kashiwa, K. Matyjaszewski, Macromoleeules 37 (2004) 3651-3658. [5] H, Kaneko, S. Kojoh, N. Kawahaia, S. Matsuo, T. Matsugi, "H. Kashiwa, J. Polym. Sci. Part A; Polym. Chem. 43 (2005) 5103-5118. [6] H. Kaneko, S. Kojoh, N. Kawahara, S. Matsuo, T. Matsugi, N. Kashiwa, Macromol. Symp. 213 (2004) 335-345. [7] N. Kashiwa, S. Kojoh, N. Kawahara, S. Matsuo, H. Kaneko, T. Matsugi, Macromol. Symp. 201(2003)319-326. [8] J. Imuta, Y. Toda, N. Kashiwa, Chem. Lett. (2001) 710-711. [9] J. Imuta, N. Kashiwa, Y. Toda, J. Am. Chem. Soc. 124 (2002) 1176-1177.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

7

Japanese National Project for the Innovation of Industrial Polypropylene Process Technology Minora Terano8"*, Keigo Suehiro\ Takehiro Sagaec, Etsuo Tobitad a

Japan Advanced Institute of Science & Technology, Nomi, Ishikawa, 923-1292, Japan Mitsui Chemicals, Inc., Minato-ku, Tokyo, 105-7117, Japan c Japan Polypropylene, Co., Yokkaichi, Mie, 510-0848, Japan Asahi Denka Co., Ltd., Shimhata, Minami-ku, Saitama, 336-0022, Japan

Abstract Japanese national project relating to the innovation of industrial polypropylene process technology has been conducted in order to depress the CO2 emission. Various new technologies including highly active catalyst with large particle size and effective stabilizer for polymerization stabilization have been successfully developed for the purpose. 1. INTRODUCTION The Kyoto Protocol came into force on February 16,2005 with 141 countries in order to reduce the emission of green house gases (mainly CO2). Japanese national project relating to the innovation of industrial polypropylene (PP) process technology named Simple Plastic Manufacturing (SPM) project has been conducted for 3 years using totally about 15 million US dollars. The main target of the project was to reduce the energy consumption of the industrial PP process in order to depress the CO2 emission [1,2]. Pelletizing step has been known to consume about 40% of total production energy in the process [1,2]. Therefore, SPM project was tried to establish the technologies to omit the pelletizing step. PP powder having good morphology, mechanical strength and high stability should be produced without pelletizing. Highly advanced catalyst and stabilization technologies were mainly required for the purpose.

M. Terana et al.

2. RESULTS AND DISCUSSION 2,1. Outline of SPM project SPM project was consisted of 2 groups aiming to develop the technologies for 2 PP grades, mjection and film. Amount of PP for injection molding grade used in Japan for various products from small-sized daily necessities to large-sized industrial materials is 1.55 million tons per year, which corresponds to ca.52 % of total PP production in Japan. Therefore, if the pelletizing step can be omitted, a great amount of energy can be saved. Fig. 1 shows the schematic diagrams of current and SPM processes for injection grade. Not only pelletizing step but compounding step can be skipped by establishing the direct compounding technology.

Current (a) Current propylene catalyst

PP Plant

propylene ethylene

Injection Plant

powder

Polymerization

(b) SPM propylene catalyst

filler pigment

stabilizer pellet

Pelletizing

product pellet

Compounding V

PP Plant propylene ethylene

Injection Injection

,

Injection Plant stabilizer filler pigment

powder

product

Compounding Direct Compounding

Polymerization

Injection Injection

Fig.l Schematic diagrams of Current and SPM processes for injection grade

2, Japanese National Project for the Innovation of Industrial PP Process Technology 9 (a) Current 1

'

FilmPlaat

Film

\

Polymerization

Extrusion & Stretching

Pelletizinn

(b) SPM

PP& Film Plant

Direct Powder Extrusion Film

Polymerization

Film Plant w connected-with PP plant.'

Extrusion & Stretching

Fig,2 Schematic diagrams of Current and SPM processes for film grade

More than 0.5 million tons of film grade PP have been produced per year in Japan. Thus, large energy saving effect was expected to achieve by SPM project. Fig. 2 shows the schematic diagrams of current and SPM processes for film grade. In SPM process, polymerization vessel and processing machine are directly connected in one factory, by which transportation of PP between the factories can be omitted in addition to the pelletizing step. It will highly contribute to reduce the energy consumption. 2.2. Catalyst technologies In order to omit the pelletizing process, highly advanced catalyst technology must be applied to generate PP powder having the same level of morphology and particle size as pellet. Impact copolymer made by in situ mixing of homo-PP and ethylene-propylene rubber in the reactor is quite important for the recent injection molding applications. When the conventional Ziegler-Natta catalysts are applied for the impact copolymer production, the producible amount of rubber is limited because of poor powder morphology and fouling in the reactor. Metallocene catalyst system discovered by Kaminsky in 1980 [3] can solve the problem by producing the polymers having narrow molecular weight and composition distributions without generating the low molecular weight and low temperature

10

M. Terano et al.

extracted components. For SPM project, the metallocene compound was combined with unique clay support-activator to produce spherical polymer. It became possible to control the morphology and particle size of PP powder by controlling the clay morphology and particle size [4]. Fig.3 shows the polymer with 2-3mm diameter produced using the clay supportactivator with 50-70 fi m in diameter.

Support-Activator Dp=50-70^.m

Polymer Dp=2-3mm

Fig.3 Morphology control for injection grade with metallocene catalyst

In the case of film grade, existing highly active Ziegler-Natta catalyst technology was applied to achieve the target morphology. Catalyst support was mechanically classified to get larger and more uniform particles. (Fig.4) 100 90

Accumulated Volume(%)

80

Original

70 60 50

Classification, 60 % recovery

40

Classification, 75%revovery

30 20 10 0 20

40

60

80

100 100

120

140

160

180

200

Support Diameter ((/an) µ m)

Support Dp=80-90/im

Polymer Dp=2-3mm

Fig.4 Morphology control for film grade with Ziegler-Natta catalyst

2. Japanese National Project for the Innovation of Industrial PP Process Technology 11 2.3. Stabilization

technology

PP is known to degrade easily via thermo- or photo-oxidation [5] . Therefore, stabilizers have to be added to PP typically in the pelletizing process in order to prevent the degradation. The palletizing is very important from this viewpoint, but the process consumes huge energy. In order to stabilize PP without pelletizing, new technology with low energy consumption should be developed. Several attempts for the stabilizer addition have been made for simplifying the production process or lowering energy consumption [6,7] . However, a direct stabilizer addition to the polymerization system has been regarded to cause a drastic decrease in the catalyst activity. In this study, the stabilizer was tried to add during polymerization, because the method is believed to be quite effective for energy saving. In addition, the cost reduction of PP production may be achieved at the same time by the method. Ziegler-Natta and metallocene catalysts are known to deactivate easily by various compounds having polar group. Masking of polar group seemed to be a key technology to realize the direct stabilizer addition. Antioxidant containing phenolic OH was chosen as an adequate stabilizer for this study. Phenols react with alkylaluminum to generate phenoxides, which can reproduce original phenols by hydrolysis after polymerization. Market available phenolic antioxidants were examined first, but they were found to decompose during hydrolysis. Therefore, new antioxidant, 3-(3,5-di-t-butyl-4-hydroxyphenyl)-Noctadecylpropionamide (AO-1), was developed and confirmed as a suitable compound in order to avoid the phenomenon. Tab.l summarizes the polymerization results with Ziegler-Natta and Metallocene catalysts in the presence of AO-1 phenoxide (Fig.5) made by the reaction of AO-1 with triethylaluminum.

o Fig.5 AO-1 phenoxide

No differences are found in catalytic activity and polymer characteristics such as molecular weight, polydispersity and meso pentad fraction as shown in Tab.l. It becomes obvious that the masking of OH group by alkylaluminum is quite effective to prevent the catalyst deactivation. PP powder obtained using AO-1 phenoxide was confirmed to be as stable as pellet.

12

M, Terano et at Tab.l Polymerization results with AO-1 phenoxide M

[mmmm] e '

Cat. system

Additives

Yield c>

Ziegler-Natta a*

Non

9400 7100 9100

40 39 40

4.8 5.1

97.1 97.0 97.2

24000 8000 23000

4.6 4.4 4.6

2.0 1.9 2.0

86.9 87.8 86.6

AO-1 AO-1 phenoxide Metalloceneb^

Non AO-1 AO-1 phenoxide

Mw- 1C

% 5.1

) heptane slurry, Tp=70aC, Pp= O.SMPaG, 1h b> toluene slurry, , Pp= O.SMPaG, 1h > g-PP/g-cat. for Ziegler-Natta, kg-PP/mol-Zr-h for metallocene "' measured by GPC ' rneso pentad fraction by "C-NMR

c

3.CONCLUSIONS New catalyst and stabilization technologies were successfully developed to omit the pelletizing step, which will contribute to the innovation of industrial PP process with low energy consumption leading to depress the CO2 emission. Acknowledgements This work was supported by NEDO (New Energy and Industrial Technology Development Organization). References [1] Simple Plastic Manufacturing (SPM) Project, 2005: http://www.nedo.go.jp/ iinkai/kenkyuu/bunkakai/17h/jigo/4/l/index.html [2] M. Terano, E. Tobita, O. Segawa, T. Sagae, M. Ohgizawa, Expected Materials for the Future, 4 (2004) 28-35. [3] T. Tayano, M. Sugawara, MetCon2000 (Jun. 8-9,2000, Houston). H. Uchino, Polypropylene 2001, (Sep.l 1-13,2001, Zurich). [4] H. Sinn, W. Kaminsky, Adv. Organomet. Chem.18 (1980) 99-149. [5] H. Zweifel, Stabilization of Polymeric Materials, Springer, Berlinl (1998) pp.10. [6] for example, EP0254348 A2, Enichem, JP 2991751, Himont. [7] N. Kawamoto, T, Horikoshi, K. Nomura, H. Yokota, Y. Negish, E. Tobita, M. Terano, J. Appl. Polym. Sci. 99 (2006) 1350-1358.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

13

Novel Energy and Cost Saving Polypropylene Stabilization via Addition of Antioxidant into Polymerization System Hideyuki Yokota,a Kazukiyo Nomura,8 Takahiro Horikoshi,a Yoshinori Negishi,a Naoshi Kawamoto/ Etsuo Tobita,*a Minoru Teranob "Polymer Additives R&D Laboratory, ASAHIDENKA Co., Ltd, 5-2-13, Shirahata, Minami-ku, Saitama City, Saitama, 336-0022, Japan b Japan Advanced Institute of Science and Technology, 1-1, Asahidai, Nomi City, Ishikawa, 923-1292, Japan

Abstract Polypropylene powder stability was evaluated by means of biaxially-oriented film processing, where the powder were prepared by using Ziegler catalyst in the presence of aluminum phenoxide derived from 3-(3,5-di-f-butyl-4hydroxyphenyl)-N-octadeeylpropionamide (AO-1) and triethylaluminum. Despite the lower concentration of antioxidant (ca. 560 ppm), the powder exhibited excellent stability compared with commercial film grade pellet including antioxidants of over 1000 ppm. Half amount of loading was found to be sufficient in the case of AO-1 phenoxide added into polymerization system. This indicates that cost saving of antioxidant due to the reduction of loading level can be achieved by the method. Thus, the method used the AO-1 phenoxide in the polymerization system is effective and economical technology. 1. INTRODUCTION Since the PP production energy savings was considered to contribute to the reduction of carbon dioxide emission, NEDO (New Energy and Industrial Technology Development Organization, Japan) promoted the energy reduction project on PP production technology via excluding pelletizing process, which was named as SPM (Simple Plastic Manufacturing) project [1], In the course of

14

H. Yokota et at

our studies, it was demonstrated that the stabilization via the phenolic antioxidant addition as an aluminum phenoxide into slurry and bulk polymerization instead of pelletizing was quite effective [2-5]. AO-1 (3-(3,5di-f-butyl-4-hydroxyphenyl)-N-octadecylpropionamide) was designed as a suitable phenolic antioxidant for the use in the polymerization system from the standpoint of avoiding the decomposition via masking with aluminum alkyls. Thus, excellent additive-dispersion throughout the PP powder by the method enables us the superior stability. From the viewpoint of industrialization of this method, it is important whether cost saving can be achieved via this method or not. Since this method provides superior stability of PP powder, there is a possibility of the reduction of the additives-loading amount, resulted in cost saving of additives even with pelletizing process. In this study, the powder stability via the method was evaluated in comparison with that of commercial standard PP pellet. Biaxially-oriented film processing was conducted in this study, where PP encounters higher processing temperature and higher shear under the atmosphere, since the reduction possibility of additives-loading was considered to be actually estimated under severe conditions, 2. EXPERIMENTAL Sample was prepared by bulk polymerization with a supported Ziegler catalyst in combination with triethylaluminum and cyclohexylmethyldimethoxysilane (Al/Si/Ti=250/4/l) at 70 °C for 1 h in the presence of AO-1 phenoxide [1]. Additionally, AO-1 of 560 ppm was dry-blended under nitrogen atmosphere to powder polymerized without phenoxide under the same above conditions. These samples were extruded at 230 °C under nitrogen atmosphere, followed by sheeting and drawing, and then changes in molecular weight of the biaxiallyoriented films (BOPP) were evaluated by size exclusion chromatography (SEC) [1,4], Commercial film grade pellet containing conventional antioxidants of over 1000 ppm was also processed and evaluated. 3. RESULTS AND DISCUSSION The stability of PP powder via the addition of AO-1 phenoxide into polymerization system was evaluated in order to estimate the possibility of cost saving via the method using AO-1 phenoxide. Two powder samples were prepared by bulk polymerization. One powder sample was prepared by traditional method, in which AO-1 was dry-blended under N2 after polymerization. Another one was prepared by the method, where AO-1 phenoxide was added into polymerization system. Stability during film processing as BOPP was evaluated by SEC as changes in molecular weight.

3, Novel Energy and Cost Saving PP Stabilization via Addition ofAntioxidant

15

Figure 1 shows the changes in molecular weight of bulk-polymerized samples at each processing stage. Here, both samples contained AO-l of 560 ppm, respectively. The molecular weight of the sample prepared by dry-blend was slightly decreased by extrusion as a first step of processing, but the magnitude was minimal. Drastic decrease in molecular weight (over 7 %-decrease) was observed during sheeting. Molten polymer encountered higher shear rate and was exposed by oxygen in atmosphere at higher temperature. This was considered to lead to drastic degradation of the sample. At drawing stage, further decrease in molecular weight was found to proceed with drawing resulting in over 10 %-decreasing. Since the drawing was conducted at a temperature of below melting temperature of polymer, i.e., the moderate conditions, the magnitude in the decrease during drawing was considered to be lower than that during sheeting. 6.0 X I 0 s

4.0 X 10 s Initial Extrusion Sheeting Drawing Figure 1 Changes in Mw of samples in each processing stage. : by developed method (AO-l of 560 ppm), (o): by dry blend (AO-l of 560 ppm)

On the other hand, the sample polymerized with AO-l phenoxide (by developed method) exhibited excellent stability throughout the BOPP processing. No degradation was observed for the samples by the developed method during extrusion and drawing. Despite the cruel conditions of sheeting, degradation of the sample by the developed method was prevented effectively, and the decrease in molecular weight throughout the BOPP processing was estimated to be minimal as below 2 %. Thus, excellent stability can be achieved by the developed method even under cruel processing conditions, and the method was superior to the conventional dry-blend one in stabilization. As reported previously, superior dispersion of antioxidants throughout the PP powder was considered to give rise to the advantage in stability [1-7]. In contrast, the

16

H. Yokota et al.

antioxidant dispersion of the sample extruded by dry-blend was indicated to be insufficient. This was thought to cause the depression of the efficient and effective inhibition of degradation triggered with oxygen/heat during sheeting. Figure 2 shows the changes in molecular weight of the sample by the developed method (560 ppm as AO-1) and commercial pellet having over 1000 ppm of conventional phenolic antioxidant. Additionally, commercial pellet contained phosphite as a secondary antioxidant as well as phenolic antioxidant. Phosphite is known to provide good stability in particular during processing, and to add generally to PP together with phenolic antioxidant [6]. The commercial one degraded in particular at the sheeting stage and the magnitude in the decrease of molecular weight was estimated to be ca. 3 %. This was not so significant and was acceptable degradation levels in practical use.

O.U<**> 1U

is

5.5 X I 0s

u

5.0 X 10s

J

4.5 X10 5

a

_,

4.0 X 10s

Initial Extrusion Sheeting Drawing Figure 2 Changes In Mw of samples obtained by the developed method and standard pellet in each processing stage. : by developed method (AO-1 of 560 ppm), (o): commercial pellet (conventional antioxidant of over 1000 ppm)

As mentioned above, the decrease in molecular weight of the sample by the developed method was estimated to be less than 2 %. It should be noted that the stability of the sample by the developed method was superior to that of commercial one, because the sample contained only phenolic antioxidant of 560 ppm: the content was about half of that of commercial one and without phosphite. This indicates that excellent stability can be achieved by the developed method with lower-loading level compared with conventional dry blend method. Considering these results, half amount of phenolic antioxidant is at least suggested to be sufficient for stabilization of PP in the case of the use of the developed method. In addition, suitable usage of phosphite and calcium

3. Novel Energy and Cost Saving PP Stabilization via Addition ofAntioxidant

17

stearate in combination of AO-1 phenoxide by the developed method is believed to promote the further reduction of total loading-amount of additives. Thus, the cost saving concerning additives via the developed method is estimated to be above 30 % including of cost of aluminum alkyls as masking agent for phenolic antioxidant, AO-1. Furthermore, no additional installation of heavy equipment was necessary for the existing PP plant because the additives can be fed into reactors via cocatalyst feeding system or vessels, and then no investment for expensive equipments was necessary to apply the developed method to the existing plant. In other words, the developed method has an excellent retrofitability. The developed method enables us not only to reduce the carbon dioxide emission due to excluding the pelletizing process but also to minimize the loading-amount of additives resulting in saving PP production cost. The method is believed to be competitive technology instead of pelletizing, and to contribute further progress of polypropylene industry. 4. CONCLUSIONS Polypropylene obtained by the developed method with AO-1 phenoxide exhibited excellent stability under cruel processing conditions as biaxiallyoriented film processing. Below half loading-amount was suggested to be sufficient for stabilization by using the developed method, that is, the significant reduction in additives-loading amount was indicated to be achieved by the method. The estimated cost saving of additives loading is over 30 %-reduction of conventional dry-blend method with pelletizing. Thus, the method is competitive stabilization technology. Acknowledgements The study was supported by Grand-in-aid for the Simple Polymer Manufacturing (SPM) Project (2002-2004) of New Energy and Industrial Technology Development Organization (NEDO), Japan, References [1] Simple Plastic Manufacturing (SPM) Project, 2005: http://www.nedo.go.ip/ imkai/kenkvuu/bunkakai/17h/iigo/4/l /index.html [2] M. Terano, E. Tobita, O. Segawa, T. Sagae, M. Ohgizawa, Expected Materials for the Future 4 (2004) 28-35. [3] N. Kawamoto T. Horikoshi, K. Nomura, H. Yokota, Y. Negishi, E. Tobita, M. Terano, J. Mater. Life Soc. 17 (2005) 61-66. [4] N. Kawamoto, T. Horikoshi, K. Nomura, H. Yokota, Y. Negishi, E. Tobita, M. Terano, J. Appl. Polym. Sci. 99 (2006) 1350-1358.

18

H. Yokotaetal,

[5] M. Terano, N. Kawamoto, T. Horikoshi, K. Nomura, H. Yokota, Y. Negisbi, E. Tobita, J. Mater. Life Soc. Symposia 2005, 67-68. [6] K. Schwarzenbach, B. Gilg, D. Mueller, G. Knobloch, J.-R. Pauquent, P. Rota-Graziosi, A. Schmitter, J. Zingg, E. Kramer in: H. Zweifel (Ed.), Plastics Additives Hanser, Munich 2000, p. 14.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

19

Polymerization Behavior with Metallocene Catalyst Supported by Clay Mineral Activator Hiroshi Nakano,* Tadashi Takahashi, Hideshi Uehino, Takao Tayano, and Toshihiko Sugano Polymerization Technical Center, Japan Polypropylene Corporation 1, Toho-cho Yokkaieki, Mie, 510-0848 JAPAN, email:[email protected]

Abstract Acid treated clay (montmorillonite) was reacted with AlEt3 (TEA) to give TEA-treated montmorillonite (TEA-Montmorillonite). Various amounts of 2,6-dimethylpyridine (26DMP) was added to TEA-Montmorillonite in order to control the acid strength of TEA-Montmorillonite, then the reaction mixture was reacted with triisobutylaluminum (TiBA) (O.fimmol) and 0.3mmol of racMe2Si(2-Me-4-Ph-l-Ind)aZrCl2 (1) to prepare the catalyst. The catalysts were characterized by using solid state UV-vis spectrum spectroscopy. Ethylene polymerizations and propylene-ethylene (1:1 molar ratio) copolymerizations were carried out in heptane at 75 °C-0.8 MPaG for 0.5 h after prepolymerization. The effect of acid strength and propylene prepolymerization on the olefin polymerization behaviors were studied in this catalyst system. 1. INTRODUCTION Since the discovery of MAO-metallocene catalyst system by Sinn and Kaminsky, metallocene catalysts have given to the chemist the opportunity to control the catalytic features by the design of metallocene complex. [1] The cocatalysts have also been developed to control the catalytic features such as activity, selectivity, and molecular weight. [2-5] Clay mineral is one of the most attractive cocatalyst for the olefin polymerization because of its abilities of activating metallocene without MAO.[6-12] From the other view point, this

20

H. Nakano et al

material has attracted much attention as a modifier of the polyolefin to make clay-polymer nanocomposite.[13-20] As a co-catalyst, the clay mineral has superior characteristics such as stability and inflammability, in contrast to MAO which is reactive to air and moisture. In addition, clay mineral could be used as a catalyst support for the production of polyolefins, therefore the clay mineral cocatalyst is called "Support Activator." In this paper, we will show the preparation and characterization of metallocene catalyst supported by clay mineral activator and discuss the results of the ethylene polymerization and ethylene-propylene co-polymerization, 2. EXPERIMENTAL Acid treated clay was prepared by the treatment of clay (montmorillonite) with the solution of sulfuric acid. Treated clay was washed with water to pH>3 and dried in vacuum at 200 °C. The clay was reacted with heptane solution of AlEtj (TEA) under nitrogen, and then rinsed with heptane to give TEA-treated montmorillonite (TEA-MontmoriEonite). Various amounts of 2,6dimethylpyridine (26DMP; Oumol/g-clay for Cat.l, 80 umol/g-clay for Cat.2, and 200 umol/g-elay for Cat.3) was added to the slurry of TEAMontmorillonite (20 g) in order to control the acid strength of TEAMontmorillonite, then the mixture was reacted for lh with triisobutylaluminum (TiBA) (0.6 mmol) and 0,3 mmol of rac-Me2Si(2-Me-4Ph-l-indenyl)2ZrCl2 (1) to give the catalyst (Cat.1-3). The Cat.1-3 were treated with propylene monomer (C3He/Cat.=2.0wt/wt) in heptane, and then the solvent was removed to give Pcat.1-3, respectively. Ethylene polymerizations and propylene-ethylene (1:1 molar ratio) copolymerizations were carried out in heptane at 75 °C-0,8 MPaG for 0,5 h after prepolymerization. 3. RESULTS AND DISCUSSION 3.1. Acid strength and catalysis feature Acid strength of clay mineral, in this article this means the acid strength of the strongest acidic sites on each clay mineral, should be controlled by amount of the added base, 26DMP. The base would react with strongest acidic sites to poison the acidic site. Therefore addition of smaller amount of base should retain stronger acidic site and the resultant acid strength will be in the order of Cat.1 (strong) >Cat.2 (intermediate) >Cat.3 (weak). The TEAMontmorillonite with no 26DMP, which is used for the synthesis of Cat.1, exhibits an acidic coloration by addition of benzeneazodiphenylamine as acid-

4. Polymerization Behavior with Metallocene Supported by Clay Mineral Activator

21

Absorbance

base indicator. This means that this clay mineral has an acidic site of pKa less than 1.5. Addition of 80umol/g-elay of 26DMP, which amount corresponds to that for Cat.2, makes disappearance of the acidic coloration. This indicates that Cat.2 has an acidic site of pKa equal to about 1.5. Figure 1 shows solid state UV-vis spectrum of catalyst, indicating that the Cat.1 with strong acidic site has two peaks. The calculation by density function theory result[21,22] shows that the peak with shorter wavelength is assigned to a neutral zirconium species, such as "ZrCl2" or "ZrR2", and the peak with longer wavelength is assigned to a 0.5 cationic Zr species. These Cat.1 0.4 Cat.2 results indicate that strong Cat.3 acidic site of pKa<1.5 has an 0.3 ability to cationize 0.2 metallocene complex. On the other hand, the Cat.2 with 0.1 intermediate acidic site of 0 pKa=1.5 and Cat.3 with weak 300 400 500 800 500 600 600 700 acidic site show only peak Wavenumber [nm] with shorter wavelength Figure 1. Solid state UV-vis spectra of Cat.1-3 assigned to neutral Zr-species. Figure 2 shows the zirconium content of prepolymerized catalysts. The catalyst with strong acidic site has a high Zr-content. This would indicate that the strong acidic site makes a tight bonding between metallocene complex and clay, to give higher Zr-content of the catalyst.

Zr content [[µmol/g-clay]

15 »

M 10

1 5

\

8

N

0 0

50

100 100

150

200

[umol/g-clay] 26DMP [µmol/g-clay] Amount of 26DMP

Figure 2. Relation between acid strength and Zr content in Pcatl-3

22

if. Nakano et al.

3.2. Effect ofpropylaie prepolyinerizafioii We performed prepolymerization before polymerization studies. Figure 3 shows the solid state UV-vis spectrum of prepolymerized catalysts (Pcatl-3). The Pcat.l has substantially only one peak of cationic Zr species. Before prepolymerization, the Cat.2 has no cationic Zr species, but after prepolymerization Pcat.2 has cationic Zr species. These results indicate that the prepolymerization accelerates cationization of metallocene complex. 0.5

Pcat.1 Pcat.2 Pcat.3

Absorbance

0.4

e <

0.3 0.2 0.1 0 300

400 500 600 700 [nm] Wavenumber [nm]

800

Figure 3. Solid state UV-vis spectra of Pcat.1-3

We studied a side reaction of metallocene cation with TiBA. The CatlM was prepared by the same method as Cat.l except for using dimethyl-complex, racMe2Si(2-Me-4-Ph-1 -Ind)2ZrMe2, CatlM Cat.1M instead of the reaction mixture of 1 —Cat.1M+TiBA CatlM+TiBA and TiBA. CatlM was reacted PcatlM Pcat.1M with TiBA. The solid state UV-vis PcatlM+TiBA Pcat.1M+TiBA spectrum of resultant catalyst is 0.5 \\ shown in Figure 4. This catalyst 0.4 has no signal of cationic Zr species. This would indicate that cationic Zr §0.3 0.3 complex in CatlM was reacted £0.2 0.2 with triisobutylaluminum to give other unknown compound. CatlM 0.1 has a very low activity in propylene 0 polymerization. This would be 300 400 500 600 700 800 800 300 attributed to such side reaction of Wavenumber [nm] CatlM with a scavenger of TiBA Figure 4. Solid state UV-vis spectrum in polymerization reactor. The CatlM was prepolymerized by the Abso rbance

V

4. Polymerization Behavior with Metallocene Supported by Clay Mineral Activator

23

same manner as Cat.1 to give PcatlM. The solid state UV-vis spectrum of PcatlM and its TiBA added catalyst are shown In Figure 3. Both spectra are very similar, indicating that PcatlM is not reacted with TiBA. 3.3. Polymerization

,000 1,000

20,000

900

18,000 18,000 16,000 16,000

PE activity [g/g-cat/h]

800 600

14,000 14,000 12,000 12,000

500 500

10,000 10,000

400 400 300 300

8,000 6,000

200 200 100 100

4,000 2,000

700 700

0 0

0

50

100 100

150 150

E PR activity [g/g-cat/h]

Figure 5 shows the relationship between an activity and an acid strength of clay mineral in the catalyst. The X-axis indicates an amount of added 26DMP per gram clay, where smaller amount of 26DMP gives stronger acidic site of clay. The activities of polyethylene (PE) and ethylene-propylene copolymer (EPR) decrease with decreasing the acid strength. If the acidic site affects only cationization of metallocene complex, both of suitable acid strength range should be the same. But suitable acid strength range about EPR activity is narrower than that of PE. These results will indicate that the acidic site influences not only the cationization, but also the nature of active site.

0 200

[umol/g-clay] Amount of 26DMP [µmol/g-clay]

Figure 5. Acid strength of catalyst and activities

4. CONCLUSIONS Clay with strong acidic site has an ability to cationize metallocene complex. Strong acidic site makes a tight bonding between metallocene complex and clay, to give higher Zr-content of the catalyst and higher activity of ethylene polymerizations and propylene-ethylene copolymerization. Prepolymerization accelerates the cationization of metallocene complex and makes the claycatalyst stable to the reaction with TiBA. Suitable acid strength range about activity depends on the monomer species. This study indicates that not only acid strength but also propylene prepolymerization are important for cationization of metallocene complex,

24

K Nakano et al

interaction between metallocene cation and clay mineral, stability of metallocene cation, and polymerization activity. References [I] E. Y.-X. Chen, T. J. Marks, Chem. Rev., 100 (2000) 1391. [2] H. W. Turner, G. G. Hlatky and R. R. Eckmann, J. Am. Chem. Soc. 111 (1989)2728. [3] X. Yang, C. L. Stem and T. J. J. Marks, J. Am. Chem. Soc. 113 (1991) 3623. [4] K. Soga and M. Kaminaka, Macromol. Chem. 194 (1993) 1745. [5] Y. Suga, Y. Maruyama, E. Isobe, T. Suzuki, F. Shimlzu, U.S. Patent 5308811(1994). [6] Y. Suga, Y. Uehara, Y. Maruyama, E. Isobe, Y. Ishihama and T. Sagae, U.S. Patent 5973084 (1999). [7] T. Suzuki and Y. Suga, Polym. Prepr. 38 (1997) 207. [8] T. Suzuki, E. Isobe and Y. Suga, Polym. Prepr. Jpn. 47 (1998)1629. [9] Y. Suga, T. Suzuki, T. Sugano, T. Tayano, and F. Shimizu, Kobunshi Ronbunshu 59 (2002)178. [10] T. Takahashi, H. Nakano, H. Uehino, T. Tayano, T. Sugano, ACS Polymer Preprints 43 (2002) 1259. II1] K. Weiss, C. Wirth-Pfeifer, M. Hofmann, S. Botzenhardt, H. Lang, K. Bruning, E. Meichel, J. Mol. Catal. A 182-183, (2002) 143. [12] D. W. Jeong, D. S. Hong, H. Y. Cho, S. I. Woo, J. Mol. Catal. A 206 (2003)205. [13] H. L. Qin,Q. S. Su, S. M. Zhang, B. Zhao, M. S. Yang, Polymer, 44 (2003) 7533. [14] T. Sun, J. M. Garces, Advanced Materials, 14 (2002) 128. [15] T. Sun, J. M. Garces, Catal. Commun. 4 (2003) 97. [16] S.-W. Kuo, W.-J. Huang, S.-B. Huang, H.-C. Kao, F.-C. Chang, Polymer 44 (2003) 7709. [17] C. Y, Lew, W. R. Murphy, G. M. McNally, Polymer Engineering and Science, 44 (2004) 1027. [18] Z. M. Wang, H. Han, T. C. Chung, Macromolecular Symposia, 225 (2005) 113. [19] H.-T. Liao, C.-S. Wu, J. Appl. Poly. Sci. 97(2005) 397. [20] N. Ristolainen, U. Vainio, S. Paavola, M. Torkkeli,R. Serirnaa, J. Seppaelae, J. Poly. Sci. B 43 (2005) 1892. [21] H. Uehino, H. Nakano, S. Toriu, S. Tabata, Y. Kurata, J. Endo, Polymer Prep. Jpn. 51(2002)1623. [22] D. Coevoet, H. Cramail, A. Deffieux, Macromol. Chem. Phys. 199 (1998) 1451.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

25

Regulating the Structure of Ethylene-Propylene Copolymer for Polyolefin In-reactor Alloy with Improved Properties Qi Dong, Na Li, Xiaofeng Wang, Zhisheng Fu, Junting Xu, Zhiqiang Fan* The Institute of Polymer Science, Zhejiang University, Han^hou 310027, China Abstract Ethylene-propylene copolymers were synthesized with TiCl4/MgCl2/diester type high-yield supported catalysts. Composition distribution and chain structure of the copolymer were studied by fractionating the product into noctane soluble and insoluble parts and characterizing the fractions by 13C NMR and thermal analysis. The «-octane insoluble part is a kind of segmented copolymer. It is proposed that segmented copolymer fractions found in PP/EP in-reactor alloy are formed during the copolymerization stage. Differences in catalyst, cocatalyst and addition of hydrogen were found to strongly influence the composition distribution and chain structure of the copolymer. 1. INTRODUCTION In-reactor blending is an important way of enhancing performances of polyolefin. High-impact polypropylene made by sequential propylene polymerization and ethylene-propylene copolymerization (PP/EP in-reactor alloy) has been produced in large scale since the 1980's [1]. It is well known that the multi-phase structure and synergistic effects between the different phases of in-reactor alloys are the main reason for their high performances. However, there is still big space of further improving the structure and properties of polyolefin in-reactor alloys [1,2]. To make progress in this direction, regulating and optimizing the chain structure of the alloy are of key importance, and knowledge of the structure-properties relationship is also

26

Q. Dong et al.

inevitable for finding the optimum structure. In previous studies, chain structure of the copolymer components has been found to be the main factor that determines the phase structure and mechanical properties of the alloy [3]. However, the chain structure of EP copolymer and its correlations with the catalyst system and polymerization conditions have been scarcely reported before [4,5]. In this paper, chain structure of EP copolymer synthesized by TiCLi/MgCla/diester type high-yield supported catalysts is studied, and possible ways to regulate the structure of PP/EP in-reactor alloy will be discussed. 2. EXPERIMENTAL J.I Copolymerization Three kinds of TiCLt/MgC^/diester type high-yield supported catalysts are used in this work, which are named as Cat-A, Cat-B, and Cat-C. The titanium content of the catalysts was found to be 2~3 wt%. Ethylene-propylene copolymerization was conducted in a 300-mL cylindrical reactor (or in a 1L autoclave), which was purged with nitrogen for three times and then filled with certain volume of hydrogen (when needed) and ethylene/propylene mixture to latm. At the set temperature, 100~300ml w-heptane as solvent, a certain volume of cocatalyst (A1(C2H5)3 (TEA) or A1(I-C4H9)3 (TIBA)) and external donor in n-heptane were added in that order under stirring. 30 mg catalyst was added into the reactor after lmin, then more monomer gas was pressed into the reactor to reach the designed pressure, and the copolymerization was started at this moment. The monomer gas was continuously supplied into the reactor to maintain a constant pressure during the reaction. After 30min, the pressure was released and the polymer slurry was poured into plenty of ethanol containing HC1 to terminate the reaction and settling down the copolymer. The copolymer was filtered, washed with ethanol and vacuum dried at 50 °C. 2.2 Copolymer fractionation The copolymer was at first dissolved in boiling «-octane. The solution was slowly cooled to room temperature and a part of copolymer precipitated as gellike solid. The insoluble fraction was then separated from the solution by centrifuging. The soluble fraction was recovered by precipitation in isopropanol. 2.3 Copolymer characterization 13 C NMR spectra of the polymers were recorded in C2D2CI4 at 120 °C on a Varian Mercury Plus 300 spectrometer operating at 75 MHz. Conditions: 5 mm probe; 90° pulse angle; acquisition time 1.5 s and pulse delay 3.0 s. Approximately 3 mg of chromium(IIl) acetylacetonate was added in the sample to reduce 71. Differential scanning calorimetry (DSC) analysis was performed on a

5. Regulating the Structure ofEthylene-Propylene Copolymer for In-reactor Alloy

27

Perkin-Elmer Pyris 1 instrument. The polymer (about 4 mg) was sealed in aluminum crucible, which was then sealed in a glass tube at argon atmosphere. The glass tube was immersed in an oil bath and heated to 180 °C, kept at that temperature for 30 min, and then annealed at 140,130, 120, 110,100, 90, 80, 70, 60 and 50 °C, respectively, each for 12 h. The treated samples were then scanned in DSC from 50 to 180 °C at a heating rate of 10 °C/min. 3. RESULTS AND DISCUSSION 3.1. Composition distribution of copolymer A series of ethylene-propylene copolymer samples were synthesized using Cat-A, Cat-B and Cat-C, and the products were all fractionated into H-octane soluble and insoluble fractions. As shown in Table 1, in all the samples the noctane insoluble fraction exceeded 8 % of the product. The content of the insoluble part also increases with increasing ethylene content of the monomer feed. Table 1 Results of ethylene-propylene copolymerization with different catalysts Sample

Catalyst

C3:C2 in feed

Activity (kg/gTi-h)

M-C8 insoluble part c (wt-%)

(mol/mol) 1 Cat-A 1:1 9.18 13.7 13.4 1:1 Cat-B 17.3 2 3 7.77 1:1 19.4 Cat-C 6.95 2:1 S.12 Cat-A 4 2:1 9.08 Cat-B 9.16 5 5.54 2:1 14.7 Cat-C 6 a Polymerization conditions: solvent («-heptane) = 100 mL, catalyst = 30 mg, TEA as cocatalyst, ALTi = 200 mol/mol, Ph2Si(OMe)2 as external donor, Si/Ti = S mol/mol, monomer pressure = 1 bar, 60 °C , 0.5 h. b Molar ratio of propylene to ethylene in the monomer feed. e Weight percentage of the H-octane insoluble fraction.

To find the differences in chain structure of the soluble and insoluble fractions, their sequence distribution were determined by 13C NMR, and the results are shown in Table 2. It is clearly seen that the insoluble fraction is a kind of segmented copolymer, which contains many long PE and PP segments and can be partly crystallizable. The soluble part, on the other hand, shows nearly random sequence distribution. It should be noted that the insoluble fractions showed much higher ethylene content than the soluble part, meaning that the segmented copolymers are formed on those active centers that can incorporate more ethylene.

Q. Dong et al.

28

In previous studies on the structure of PP/EP in-reactor alloy, it has been found that partly crystalline segmented eopolymers also exist in the alloy, which account for 5~15 % of the alloy or 10~30 % of the alloy's copolymer fractions.[3] The sequence distribution of these fractions in the alloy is quite similar to that of the w-octane insoluble fraction of the copolymer, but far different from PP-6-EP diblock copolymer that might be formed during the switching from homopolymerization to copolymerization. The similarity between the DSC curves of w-oetane insoluble fraction of EP copolymer and the segmented copolymer fraction in the alloy (see Figure 1) also implies that they have the same structure. So it is reasonable to say that the segmented copolymer fractions are formed in the copolymerization stage of alloy synthesis. Table 2 Sequence distribution of the copolymer fractions a Sample

Ethylene content (%)

[EEE]

[PEE]

[PEP]

[EPE]

[PPE]

[PPP]

4 (Insoluble)

67.6

0.565

0.0§2

0.029

0.041

0.059

0.225

32

5 (Insoluble)

60.1

0.496

0.074

0.031

0.035

0.066

0.298

3B

6 (Insoluble)

48.9

0.402

0.053

0.034

0.027

0.068

0.417

53

5 (Soluble)

28.9

0.059

0.107

0.123

0.061

0.232

0.418

1.9

6 (Soluble)

29.7

0.081

0.10S

0.110

0.060

0.206

0.437

2.7

"Conditions of sample synthesis are the same as Table 1. Product of the reactivity ratios.

The data in Table 1 and Table 2 also show that the composition distribution of the copolymer changes with the catalyst in a broad range. Not only the amount of the insoluble fractions, but also their chain structure are greatly affected by the catalyst. This means that modifying the catalyst itself should be the main way to improve the structure of PP/EP in-reactor alloy. 3.2. Effect of cocatalyst on copolymer structure When the cocatalyst of the copolymerization system was changed from TEA to TIBA, strong changes in the composition distribution and sequence distribution of copolymer were found (see Table 3). The amount of insoluble part greatly increased when TTBA replaced TEA. Using Cat-C as the catalyst, more than 30% of the copolymer became insoluble. On the other hand, sequence distribution of both the soluble and insoluble parts was also much different from those of the TEA activated system (see Table 4). Replacing TEA with TIBA caused decrease of ethylene content in the insoluble part and increase of it in the soluble part. This means that changing cocatalyst may be

J. Regulating the Structure ofEthylene-Propylene Copolymer for In-reactor Alloy

29

nttuulH,

100 Ttrrpemure (°C)

Figure 1 DSC curves of fractions from EP copolymer and PP/EP in-reactor alloy

120 140 160 Tempeoture (*C)

Figure 2 DSC curves of the insoluble part of copolymers synthesized with and without hydrogen addition

Table 3 Influences of oooatalysts on copolymerization Sample

Catalyst

Activity (kg/gTi.h)

M-Cg insoluble part (wt-%)

Cat-A 7.57 19.5 Cat-B 6.64 9.00 Cat-C 6.32 32.1 "The polymerization conditions were the same as those of iamples 4-6 in Table 1, except that TIBA was used as eoeatalyst. Table 4 Influences of oocatalyst on the sequence distribution of copolymer fractions * Sequences

TEA Soluble

TEA Insoluble

TTBA Soluble

E(%)

29.79

82.72

47.33

74.25

EEE

0.068

0.682

0.143

0.533

EEP

0.129

0.112

0.204

0.164

PEP

0.101

0.033

0.126

0.046

EPE

0.078

0.048

0.122

0.052

PPE

0.364

0.049

0.205

0.129

PPP

0.261

0.076

0.199

0.077

TTBA Insoluble

b

1.80

9.32

2.08

5.81

nPc

2.70

2.38

2.34

2.22

nE

1.30 11.38 5.83 1.45 Polymerization conditions: Cat-B = 30 mg, w~heptane = 300 mL, Al/Ti = 200 mol/rnol, PhaSifOMe^/Ti = 5 mol/mol, propylene:ethylene in feed = 1.5:1, monomer pressure = 3 bar, 70 °C, 0.5 h. Average length of the ethylene segments. e Average length of the propylene segments.

run

a

30

Q, Dong et al.

an effective way to regulate the structure of both random and segmented copolymer fractions in the PP/EP in-reactor alloy. Both parts of copolymer are believed to play key roles in enhancing the impact strength of the material [3]. 3.3. Effects of hydrogen on copolymer structure Adding small amount of hydrogen (10 % of the monomer) in the copolymerization system not only reduced the molecular weight of product, but also changed its structure (see Fig. 2). It was found that the amount of insoluble part decreased with H2 addition, but the propylene content and average propylene segment length of the insoluble part was increased. The structure of the soluble part was only slightly affected by H2. 4. CONCLUSIONS In conclusion, differences in catalyst, cocatalyst and addition of hydrogen were found to strongly influence the composition distribution and chain structure of ethylene-propylene copolymer synthesized with TiCU/MgQa/ diester type high-yield supported catalysts. It is possible to modify the copolymer structure based on the knowledge of such influences, and thus improve the properties of PP/EP in-reactor alloy. Acknowledgements Financial supports by the Major State Basic Research Programs (Grant No, 2005CB623804, Gl 999064803) and SINOPEC are gratefully acknowledged. Referencei [1] P. Galli, G. Vecellio, Prog. Polym. Sci. 26 (2001) 1287. [2] G. Cecchin, G. Morini, A Pellieoni, Macromol. Symp. 173 (2001) 195. [3] Z.Q. Fan, Y. Q. Zhang, J. T. Xu, H. T. Wang, L. X. Feng, Polymer 42 (2001) 5559. [4] C. Cozewith, Macromoleeules 20 (1987) 1237. [5] T. Hayashi, Y. Inoue, R. Chujo, Macromoleeules 21 (1988) 3139.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

31

Application of High Resolution FTIR Spectroscopy in Structural Characterization of Polyethylene and Ethylene Copolymers Zhiqiang Su,a Xiuqin Zhang,aNing Kang,a Yizhuang Xu,*'b Ying Zhao," Dujin Wang,*/ Jinguang Wu,b Duanfii Xua ^State Key Laboratory of Polymer Physics and Chemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China, email: [email protected] h State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China

Abstract FTIR spectroscopy is a powerful technique for detecting the structural variation of semicrystalline polymers. Here in this paper, we report the application of high resolution FTIR spectroscopy in the structural characterization of polyethylene and ethylene copolymers, including high density polyethylene (HDPE), ethylene-vinyl acetate copolymers (EVA), and their hydrolytic products (EVOH). For ethylene copolymers, high-resolution cryogenic FTIR spectroscopy revealed that there exist polymorphism phenomena and crystalline phase transformation as experimental temperature was changed; FTIR spectral study also showed that the hydroxyl groups of EVOH enter crystalline region, while the side branches of EVA copolymers exist predominantly in amorphous region. For HDPE, based on the results of high-resolution variable temperature FTIR spectroscopy, linear correlations between IR crystalline band (730/720 cm"1) shifts and the variation of unit cell parameters of HDPE have been established. 1. INTRODUCTION The crystallization behavior of semi-crystalline copolymers is an important and intriguing area of study in the field of polymer research. Many factors, including temperature, composition and sequence distribution of polymers, the tacticity of the side branches, the hydrogen-bonding interactions between the hydroxyl groups as well as the processing conditions, may influence the phase

32

Z,Su etal,

structure of semi-crystalline copolyrners.1*2 Without an essentially complete understanding of the crystallization behavior, it is impossible to obtain adequate, predictive structure-property correlations. However, despite extensive investigations, there are still some unsolved problems concerning the crystallization process and the phase structure of the semi-crystalline copolymers. For example, the polymorphism phenomena and side group location in semicrystalline polymers, as well as the structural variation of crystalline region with temperatures are still not well understood. In this paper, we used high resolution FT1R spectroscopy to characterize the polymorphism and side group location of ethylene copolymers (EVA, EVOH), and the variation of unit cell parameters of high density polyethylene (HDPE). 2. EXPERIMENTAL Materials. EVA samples were obtained from Beijing Organic Chemical Factory and their physical parameters were listed in Table 1. Melting temperatures of each sample were measured using a Mettler DSC 822e differential scanning calorimeter at a heating rate of lK/min. EVOH samples were prepared by homogeneously hydrolyzing reaction of EVA in our laboratory. Table 1. Basic parameters of EVA and EVOH copolymers. sample EVA (9) EVA (14) EVA (18) EVA (28) EVA (40)

Co-monomer /wt% /mol% 9 14 18 28 40

3,3 5.0 6.7 11.2 17.8

d /(g/cm3)

T

T

/°c

/°c

MI /(g/10min)

0.932 0.935 0.940 0.955 0.980

98 88 84 65 49

88 72 69 52 30

2 2 3 150 50

Sample Preparation, The sample films were obtained by a method of two-step melt-pressing, i.e., the polymer pellets were first melt-pressed to form a film with a thickness of ca. 100 |j.m, then submitted for the secondary film-pressing to form the final film with a thickness of ca. 40 um. IR spectra measurement. IR spectra of EVA and EVOH samples were recorded on a Nicolet Magna 750 FTIR spectrometer with 1 cm"1 resolution and 64 scans. A MCT detector was used to acquire higher-resolution spectra. To improve spectra resolution, the cryogenic technique was applied and the temperature of the samples was controlled at ca. -194 °C during the spectra collection. In order to prevent the condensation of moisture on the surface of the

6. Application of High Resolution FTIR Spectroscopy in Structural Characterization 33

samples at low temperature, all experiments were carried out in vacuum. IR spectra of HDPE films were recorded on the same IR spectrometer with 0.125 cm"1 resolution and 64 scans. The variable temperature experiments were carried out on a Perkin Elmer's variable temperature device with NaCl windows. The samples were first cooled from room temperature to -130 DC by liquid nitrogen, and then warmed at a five-degree interval up to room temperature. During this procedure, the IR spectra were recorded. 3. RESULTS AND DISCUSSION 3.1. Polymorphism and side group location ofethylene copolymers The experimental results indicated that FTIR spectra can provide direct evidence for side groups entering the crystal lattice of ethylene segments. Through the characterization of the specific IR band variation, it was proved that the hydroxyl branch of EVOH enters the crystal lattice, while the side groups of EVA exist predominantly in the amorphous region.3 The polymorphism and the crystalline phase transformation were investigated on the two series of ethylene copolymers. It was proved that there is only orthorhombic crystalline phase for all the EVOH copolymers. For EVA copolymers, however, besides the occurrence of normal orthorhombic crystalline phase, monoclinic crystalline phase was also detected for the samples with relatively high content of side branches. Monoclinic crystalline phase is a sub-stable structure and is mainly affected by the content of the side branches and the crystallization condition. The content of monoclinic crystals dose not increase linearly with branching, but to some extent, the increase of the side branch content is propitious to the formation of monoclinic crystalline state. Different heat-treating methodologies have great influences on the polymorphism of EVA copolymers. With the increase of the annealing temperature, monoclinic crystal was gradually transformed to orthorhombic crystal. 3.2. Variation of Unit Cell Dimension of HDPE The band shift of methylene rocking vibration (720 cm"1 and 730 cm"1) of HDPE with temperature varying from -130 °C to room temperature has been characterized accurately by high-resolution FTIR. Combining with the unit cell parameters of HDPE at different temperatures, measured by Swan with wide angle X-ray diffraction (WAXD),4 the relationship between the IR band shifts of orthorhombic crystals and the variations of the unit cell parameters has been established.5 It is found that the unit cell volumes of orthorhombic crystals expand with increasing temperature, resulting in a gradual shift of methylene rocking bands to lower frequencies. In the range from -130 °C to room

34

Z Su et al.

temperature, the variations of the unit cell volume are found to have good linear correlation with the rocking bands shifts of HDPE, The calculation results showed that 1.0 cm"1 band shift for 730 cm"1 peak corresponds to 0.99% variation of the unit cell volume. As the resolution of the FT1R spectra is up to 0.125 cm"1, the tiny variation of the unit cell volume (AV) as small as 0.124 % can be accurately detected. Such a tiny variation of the unit cell volume, up to date, can not be detected by any other methods except the presently used high resolution FTIR spectroscopy. Based on the above mentioned linear correlation between 1R band shift and unit cell volume of HDPE, the variations of the unit cell dimensions of ethylene copolymers poly(ethylene-l-octene) (EG) with different octene content can also been investigated by high-resolution cryogenic FTIR spectroscopy (equations 1-3). Aa=Q,Ql-Q,068Av730 (1) Ab=-5.62xl0"4-9.7xl0"3Av730 (2) AV=1.25xl0"3-l.llxl0"2Av730 (3) 4. CONCLUSIONS High resolution FTIR spectroscopy is a powerful tool for the characterization of microstructure variation in semicrystalline polymers, including HDPE, EVA and EVOH, etc. It is not only applicable for detecting the polymorphism, crystalline phase transformation, side group location of ethylene copolymers, but also sensitive to the unit cell parameters variation in the crystalline region of HDPE. Acknowledgements The authors thank the financial support from National Natural Science Foundation of China (NSFC, Grant No. 50290090). References [1] Q, J. Zhang, W. X. Lin, Q. Chen, and G. Yang, Maeromolecules 33 (2000) 8904. [2] M. Takahashi, K. Tashiro, and S. Amiya, Maeromolecules 32 (1999) 5860. [3] Z. Q. Su, Y. Zhao, Y. Z. Xu, X. Q. Zhang, S. N. Zhu, D. J. Wang, C. C. Han, and D. F. Xu, Polymer 45 (2004) 3577. [4] P. R. Swan, Journal of Polymer Science 56 (1962) 403. [5] Z. Q. Su, Y. Zhao, N. Kang, X. Q. Zhang, Y. Z. Xu, J. G. Wu, D. J. Wang, C. C. Han, and D. F. Xu, Macromol. Rapid Commun. 26 (2005) 895.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

35

Microstructure Characterization of Polyolefms. TREF and CRYSTAF Benjamin Monrabal Polymer Char, Valencia Technology Park, a N. Capernico 10, Paterna E-46980 Spain

Abstract The introduction of single site catalysts in the polyolefins industry has opened new possibilities in polymer design through multiple reactor-catalyst systems. Very often this approach results in bimodal or trimodal composition distributions and unique composition-molar mass dependence; the performance of these resins is very sensitive to small microstructure variations. The analysis of the Chemical Composition Distribution has been, in those cases, the most important analytical task. The separation techniques being used in the characterization of the Chemical Composition Distribution, TREF and CRYSTAF, are discussed with examples for various types of polyolefins.

1. Introduction With the commercialization of Linear Low Density Polyethylene (LLDPE) copolymers in the late 1970' the Chemical Composition Distribution (CCD), or more specifically for polyethylene, the Short Chain Branching Distribution (SCBD) became the most discriminating microstructure parameter in these resins. LLDPE shows a broad non-homogeneous composition distribution attributed to the multiple site types of the supported Ziegler catalyst [1]. The importance of the SCBD on product performance has been widely discussed in the literature [2-4] and it could be expected that the producers have kept more information as proprietary know-how. Full characterization of the bivariate

36

B, Monrabal

distribution [5] did show a molar mass composition dependence with increasing molar mass as less comonomer was being incorporated; this trend related to the reactivity ratio of ethylene and comonomers is present in all LLDPE resins. With the introduction of single site catalysts in the polyolefins industry new possibilities in polymer design through multiple reactor-catalyst systems have been realized to optimize resin performance for specific applications. Very often this approach results in bimodal or trimodal composition distributions and unique composition-molar mass dependence as shown in Figure 1, representing a dual reactor resin obtained with a Ziegler type catalyst in the first reactor and a single site catalyst in the second one. The process design variables in terms of Microstructure have increased from 2 in the classical LLDPE single reactor to 5 in the dual reactor process as listed below: 1. Comonomer incorporated in Reactor 1 2. Average Molar mass in Reactor 1 3. Comonomer incorporated in Reactor 2 4. Average Molar mass in reactor 2 5. Mass ratio of resins produced in both reactors The effects of these variables on the microstructure are described in Figure 1 (meanwhile the MWD does not show significant differences). The SCBD per se is the most discriminating structural parameter in these resins and small changes may have a significant influence on properties. The possible variations in molar mass - composition dependence in these design products demand, to fully characterize them, the whole bivariate distribution (3D plots) or the simplified plots of the SCBD with molar mass dependence as shown in Figure 1. CM/3L

CH3/1000C

Figure 1. Possible variations In the CCD and molar mass dependence of a dual reactor resin.

7. Microstructure Characterization of Polyolefins. TREF and CRYSTAF

37

2. Experimental Analytical techniques to characterize the CCD or SCBD demand a separation process by crystallizability (regularity of the chains). In Polyethylene the crystallizability becomes influenced by the number of branches and in Polypropylene by the level of tacticity and/or the incorporation of ethylene molecules into the ordered polypropylene structure. The separation process is ideally performed in solution to reduce co-crystallization effects. The technique most widely used, Temperature Rising Elution Fractionation (TREF), is based on a two step separation process: In the first cycle the dissolved polymer is precipitated, and fractions of different crystallinity segregated are deposited on an inert support in a packed column by slow cooling. In a second cycle, solvent is pumped through the column meanwhile the temperature is increased to reveal the fractions previously crystallized. A schematic diagram is shown in Figure 2.

Eluritmcyde

Figure 2. TREF diagram: Crystallization cycle and Elution cycle

This crystallization process developed in 1950 [6] was given the current name by Shirayama et al in 1965 [7] and it was widely implemented in the late 70s with the commercialization of LLDPE through the work of L,Wild [8-10]. Good reviews on the technique and applications have been published [11-15]. TREF, although very powerful, has suffered until very recently from being a tedious and slow technique, requiring more than 2 days to analyze a single sample; this prompted the search for faster techniques. In 1991 B. Monrabal patented a new approach [17], simpler and faster than TREF to analyze the CCD and named the technique Crystallization Analysis Fractionation (CRYSTAF) [18]. The analytical process is carried out into a

B. Monrabal

38

vessel during the crystallization from solution. Aliquots of the solution are being filtered and analyzed as temperature goes down to obtain the cumulative CCD curves by subtraction of the precipitated fractions as shown in Figure 3.

r

K detector

i—

n

\

\

CCD

Crystallization cycle *

Figure 3. CRYSTAF principles (left). Cumulative CCD result and first derivative (right).

With this approach 5 samples could be analyzed simultaneously in less than 7 hours. Good Reviews of the technique have been published [12,14,15]. CRYSTAF and TREF techniques share similar hardware (detectors, sample preparation...) and are becoming in some applications complementary techniques, therefore it is not surprise that a development effort has been put to combine both techniques in a single apparatus as shown in Figure 4, where the capability of a CRYSTAF instrument is extended to perform like an automated TREF by the addition of an injection valve, a pump and a TREF column.

Figure 4. CRYSTAF and TREF combined.

7. Microstructure Charactertation of Pofyolefms, TREF and CRYSTAF

39

3. Results and Discussion Both techniques CRYSTAF and TREF provide similar results in most of the polyolefin resins with the only difference that the TREF curve (obtained in the melting - elution) of polyethylenes is shifted 10 to 20°C over the CRYSTAF curve (obtained in the crystallization) due to the fact that operating conditions of the techniques are far from thermodynamie equilibrium. This shift is obviously corrected when a calibration with proper standards of known comonomer composition is applied. When analyzing combinations of polypropylene (PP) and polyethylene (PE), the significant difference in super cooling between the two resins, can make too a difference in the results obtained by TREF or CRYSTAF and there are cases where the analysis can only be resolved by TREF and other cases where CRYSTAF is the only possible option [15,16]. The crystallization and elution temperatures of PP and PE in Figure 5 indicate the overlapping and separation obtained depending on the technique being used.

Crystallization Temperatures (CRYSTAF)

HDPE 95"C

Dissolution Temperatures (TREF) EPcop

Figure 5. Analysis of polyethylene, polypropylene (Ziegler type) and ethylene propylene copolymer (EP) by CRYSTAF and TREF: effect of super cooling.

An interesting case is the analysis of a blend of a metallocene type homopolymer polypropylene, with a small amount of linear polyethylene. The TREF analysis, surprisingly, does not show a separation of the two components meanwhile the CRYSTAF analysis provides a baseline separation as shown in Figure 6. The homopolymer PP, in this case produced with a metallocene catalyst results in quite significant region errors and behaves in terms of

40

B, Monrabal

crystallization like the EP copolymer of Figure 5, approaching the elution temperature of PE in TREF and crystallizing further down that Ziegler type PP or PE as seen in CRYSTYAF. TREF crystallization rate: elution rate: m

CRYSTAF crysta 1 ization rate: 0.1 ^CJm

pp

I

PE

LA

Figure 6. TREF and CRYSTAF analysis of a blend of Polypropylene homopolymer (metallooene type) with a linear polyethylene.

When dealing with complex resins the SCBD and the MWD are not enough to define a resin and the full bivariate distribution, usually obtained with a TREF GPC combination (cross fractionation) [5] or through preparative fractionation (in TREF mode) followed by GPC analysis of the fractions [19], is required. Combining Light Scattering (LS) or viscometer detectors to CRYSTAF and TREF apparatus as in Figure 4, although not providing information on the molar mass breadth of the fractions, is still a convenient and faster alternative [20,21]. The TREF - LS of a complex dual reactor resin is shown in Figure 7 indicating that the peak at around 68°C (reactor with single site catalyst) has a higher molar mass than the LLDPE obtained with a Ziegler type catalyst.

Figure 7. TREF-LS analysis of a dual reactor resin.

7. Micrastructure Characterization of Pofyolefins. TREF and CRYSTAF

41

The incorporation of a dual band Infrared detector in the TREF and CRYSTAF instruments [22], as shown in Figure 4, allows the calculation of concentration as well as branch content (or % of PP) at every temperature. Applying this approach to the CRYSTAF analysis of Figure 6 we would have no doubts about the source of the peak at 70°C (which could be assigned to a single site catalyst resin of high comonomer content). The dual band data are shown in Figure 8; the red signal is a measurement of the concentration (CH3 + CH2) and the blue one is emphasizing the branch content (CH3). The ratio of those two signals and proper calibration result in the branch content (black), which shows that peak at 70°C, is around 330 CH3/1000C , and therefore does not correspond to a single site type resin but to pure polypropylene. The peak at 85°C corresponds as expected to linear polyethylene with close to zero CH3/1000C. IMC-

CH3/10C0C

— CH3 — CHZ+CH3 — CHSrtOOOC

ft

1

1 so

A

-PP

SB im

se

04 iw

RE

Temperature CC)

Figure S. CRYSTAF analysis of a blend of homopolymer PP and linear polyethylene with a dual band Infrared detector. The right axis corresponds to the level of branches per thousand carbons.

4, Conclusions The introduction of single site catalysts in the polyolefins industry has opened new possibilities in polymer design through multiple reactor-catalyst systems which result in complex microstructures very discriminating in composition and in composition-molar mass dependence. New CRYSTAF and TREF advanced techniques provide the microstructure identification in much simpler terms than expected from classical TREF analysis. The incorporation of LS and 1R composition detectors to TREF and CRYSTAF equipment provide additional information of composition - molar mass dependence and extended identification of complex blends.

42

B. Monrahal

References [I] [2] [3] [4] [5] [6] [7] [8]

T. Usami, Y. Goto, S. Takayama, Macromolecules 19 (1986) 2722. L. D. Cady, Plastics Engin. p.25-27, January 1987. S. Hosoda, Trends in Polymer Science 3 (1993) 265-297. A. Todo, N. Kashiwa, Macromol, Symp. 101 (1996) 301. S. Nakano, Y. Goto, J. Appl. Polym. Sci. 26 (1981) 4217. V. Desreux, M.L. Spiegels, Bull. Soc. Chim. Belg. 59 (1950) 476. K. Shirayama, T. Okada, S.I. Kita, J. Polym. Sci. part A 907 (1965). L. Wild, T. Ryle, Polym. Prepr., Am. Chem. Soc, Polym. Chem. Di¥. 18 (1977)182. [9] L. Wild, T. Ryle, D. Knobeloeh, I.R. Peat, J. Polym. Sci., Polym. Phys. Ed. 20 (1982) 441. [10] L. Wild, T. Ryle, D. Knobeloch, Polym. Prepr., Am, Chem. Soc. Polym. Chem. Div. 23, (1982) 133. II1] L. Wild, Adv. Polym. Sci. 198 (1991) 1-47. [12] B. Monrabal, in; S. Hosoda (Ed.), New Trends in Polyolefin Science and Technology, Research Signpost, 1996, pp. 126 [13] C.A. Fonseca, I.R. Harrison, Modern techniques for Polymer Characterisation, R.A. PethrickEd., 1999 pages 1-13 [14] J. B. P. Soares, A. E. Hamielec, Modern techniques for Polymer Characterisation, R,A. Pethrick Ed., 1999, pp. 15-55. [15] B. Monrabal, Encyclopedia of Analytical Chemistry, John Wiley & Sons, 2000, pp. 8074-8094. [16] B. Monrabal, P. del Hierro J. Appl. Polym. Sci., pending publication. [17] B. Monrabal, Crystallization Analysis fractionation, US Patent 5,222,390 (1991). [18] B. Monrabal, J. Appl. Polym. Sci. 52 (1994) 491. [19] B. Monrabal, International GPC Symposium, San Diego, 415-419 (1996). [20] B. Monrabal, L. Romero, International GPC Symposium, Arizona, 267274 (1998). [21] W. Yau, International GPC Symposium, Las Vegas (2000). [22] B. Monrabal, 3 rd European Conference on the Reaction Engineering of Polyolefins, Lyon (2005).

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

43

8 Ultra-high Molecular Weight Polyethylene from Slurry INSITE™ Technology Koichi Hasebe*, Akio Fujiwara, Takashi Nozaki, Koichi Miyamoto, and Harumi Watanabe Polyolefins Development Dept., Polyethylene Division, Asahi Kasei Chemicals Corporation, 2767-11 Niihama, Shionasu, Kqjima, Kurashiki, Okayama, 711-8510 JAPAN.

Abstract Ultra-Mgh molecular weight polyethylene (LJHMWPE) homopolymer was prepared with the slurry INSITE™ technology and a Tebbe reagent. The molecular weight of the homopolymer was controlled from 2 million to 10 million of Mv by the concentration of the Tebbe reagent in the polymerization process, UHMWPE copolymer of ethylene and 1-hexene was also prepared. The molecular weight of the copolymer was reached up to 6 million. Both the haze and the transparency of a sheet made of the copolymer were remarkably improved. INSITE™: Trademark of the Dow Chemical Company. 1. INTRODUCTION Ultra-high molecular weight polyolefin, in particular ultra-high molecular weight polyethylene (UHMWPE) is excellent in impact resistance, abrasion resistance, sliding properties and chemical resistance compared to widely used polyethylene, usable for sliding components, and has thus been ranked as one kind of engineering plastic.

44

K. Hasehe et al.

UHMWPE with high erystallinity is white and opaque, and has poor transparency even if formed into thin sheet or film, impairing design properties of brand name as observed in the application for ski sole. In such actual situation, UHMWPEs having excellent transparency are in demand. To improve transparency, an UHMWPE copolymer obtained from ethylene and another a-olefm (comonomer) was proposed [1]. However, low polymerization temperature was necessary to produce the UHMWPE copolymer, by which the efficiency of the production was decreased. When the copolymerization was carried out at the practical temperature in the industrial process, which Is from 70 QC to 100 QC, the molecular weight of the copolymer was too small to have the excellent abrasion resistance and friction coefficient, both of which were important characteristics of the UHMWPEs. On the other hand, it Is well known that a highly active metallocene catalyst gives an ethylene polymer which has a narrow molecular weight distribution and a uniform distribution in the composition of constituent molecules. The problem in the polymerization process using the metallocene catalyst is that the polymerization rate is generally too high at initial stages to remove the heat of polymerization efficiently, and causes local heat generation spot in the obtained polymer. Thus, part of the polymer particles reaches the melting point or higher and fuses with each other to generate a bulk polymer. In a continuous process, generation of such bulk polymer results in clogging of polymer discharge tube of a polymerization reactor, making It Impossible to remove the polymer, whereby continuous operation is disturbed. 2. EXPERIMENTAL Materials. All manipulations were carried out under a nitrogen atmosphere. All solvents were dehydrated with MS-13X before use. Tebbe reagent was synthesized from bis(cyclopentadienyl)titanium dichloride and trimethylaluminium. Polymerization catalyst from the slurry INSITE™ technology was reacted with a small amount of hydrogen before use. Polymerization procedure. Polymerization was carried out in a vessel-type reactor equipped with a stirrer. 2-Methylpropane, ethylene, the catalyst, and the Tebbe reagent were continuously fed to the reactor. The polymerization rate waslOkg-PE/h. Analytical procedure. Viscosity average molecular weight ( M v ) of polymers was calculated from the intrinsic viscosity ( [T)] ) of the polymers according to the following formula. Mv = 5.34xl0 4 x[r|] 1 - 4 9 Molecular weight distributions ( MWD ) of polyethylenes obtained were determined by gel permeation chromatography ( GPC ) with an alliance GPCV2000 ( made by Waters Inc. ) at 140 "C using o-dichlorobenzene as a

8. Ultra-high Molecular Weight Polyethylene from Slurry INSITE

Technology

45

solvent. Densities of polyethylenes obtained were determined according to the method described in ASTM D1505. Measurement of hazes of polyethylenes obtained was carried out according to the method described in ASTM D1003. Crystallinity of the polymer obtained was measured by differential scanning calorimetry ( DSC) with a DSC7 (made by PERKIN-ELMER Inc.). 3.RESULTS AND DISCUSSION Ethylene polymerization was conducted with the catalyst from slurry INSITE™ technology. The catalyst was reacted with a small amount of hydrogen in order to prevent a generation of bulk polymer as well as to keep the polymerization activity high. The Tebbe reagent was continuously fed to the polymerization reactor in order to consume the hydrogen, which was also fed as a residue of the reaction with the catalyst, by the hydrogenation reaction of ethylene, because Mv of the polymer immediately decreased by hydrogen, which was one of the strongest chain transfer reagent. The results of ethylene homo-polymerization are summarized in Table 1. The catalytic activity of the run No.l was 5000g-PE/g-cat. Mv of the polymers increased from 2 million to 10 million as the feed rate of the Tebbe reagent to the reactor increased from 0.013 mmol/h to 0.38 mmol/h. Thus, it was found that molecular weight of UHMEPW can be controlled by the feed rate of the Tebbe reagent. MWDs of the polymers obtained were independent of the feed rate of the Tebbe reagent. No bulk polymer was produced, nor was the slurry discharge tube clogged, and consequently stable continuous operation was achieved. Table 1. Ethylene homo-polymerizaitona with the slurry INSITE™ technology Tebbe Reagpnt

Mv b

/mmol/h

/10" 4

1

0.013

210

2

0.038

3 4

Run No.

Density"1

Crystallinity"

/g'cm 3

%

4.3

0.930

51

440

5.1

0.928

48

0.13

920

4.5

0.927

46

0.38

1100

4.5

0.924

42

MWD

C

"Conditions: 2-Methylpropane = 32 L/h, Cat. = 0.13 nmaol/h, Production rate = 1 0 kg-PE/h. b Mv was calourated from the intrinsic viscosity of thepolymer obtained. 6 MWD was determined by GPC usingpolystyrene standard, densities were measured with ASTM-D1505. eCrystallinities were measured usingDSC.

46

K. Hasebe et al.

The results of ethylene and 1-hexene co-polymerization are summarized in Table 2, UHMWPE copolymer was successfully synthesized by using the slurry INSITE™ technology in the presence of the Tebbe reagent. The Mv values of the polymers obtained were about 5 million. The density and the crystallinity of the polymers decreased from 0.919 g/cm3 and 37 % to 0.885 g/cm3 and 8 %, respectively, as the feed rate of 1-hexene increased from 0.35 L/h to 1.80 L/h, The haze of the polymers deceased linearly as the density decreased. Thus, it is suggested that the haze of the polymers can be controlled by the feed rate of 1-hexene, same as a usual polyethylene copolymer. Table 2. Ethylene and 1-hexene eo-polymerizaiton with slurry INSITE™ technology. Run No.

Tebbe Reagent

1-Heiene

Mv b MWD 4

e

Density

Crystallinity6

Hazef

g'cm3

%

%

/mmol/h

/L/h

/10"

5

0.045

0.35

480

4.5

0.919

37

42

6

0.075

0.35

680

4.3

0.917

37

41

7

0.100

1.10

620

4.8

0.905

17

20

8

0.150

1.80

480

5.1

0.885

i

15

"Conditions: 2-MethyIpropane = 32 L/h, Cat. = 0.13 mmol/h, Production rate =10 kg-PE/h, 'Mv was ealeurated from the intrinsic viscosity of the polymer obtained. C MWD was determined by GPC usingpolystyrene standard. ^Densities were measured with ASTM-D1505. BCry stallinities were measured using DSC. Hazes were measured with ASTM-D 1003.

4. CONCLUSIONS UHMWPE homopolymer and UHMWPE copolymer were successfully synthesized from the slurry INSITE™ technology with the Tebbe reagent. The molecular weights of the produced polymers were controlled by the concentration of the Tebbe reagent in the reactor, and Mv of the UHMWPE homopolymer increased up to 10 million. The hazes of the UHMWPE copolymers were controlled by the concentration of 1-hexene and improved up to 15%. Reference [1] T. Hayashi, T. Shiraki, A. Kato, JP-B-05-86803.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

47

Effects of Solvents in Living Polymerization of Propenewith [#-BuNSiMe2(3,6r-Bu2Flu)]TiMe2MMAO Catalyst Takeshi Shiono*, Zhengguo Cai, Yuushou Nakayama Graduate School of Engineering, Hiroshima University, Kagamiyama 1-4-1, HigashiHiroshima 739-8527, Japan

Abstract Propene polymerization was performed batch-wisely by [£~BuNSiMe2(3,6-fBu2Flu)]TiMea combined with trialkylaluminum-free modified methylaluminoxane in heptane, chlorobenzene, and the mixture of heptane/chlorobenzene (1:1 in volume) at 0 °C. The conversions were almost quantitative and the molecular weight distributions were narrow regardless of the solvent used. The livingness of the propagation chain in these solvents was confirmed by post-polymerization. The stereoregulariry of the polypropylenes obtained was strongly depended on the solvents used. The heptane system gave highly syndiotactic polymer, whereas the chlorobenzene and the heptane/chlorobenzene systems gave amorphous polymers. The 13CNMR analysis of the microtacticity indicates that the steric errors caused by miss selection of the prochiral face of propene was independent of the solvents but those caused by the isomerization of the active species via alkyl migration increased in chlorobenzene and the heptane/chlorobenzene mixture. 1. INTRODUCTION Since the discovery of metallocene catalysts, much effort has been paid to develop new organometallic compounds for polymerization catalysis, so-called single-site catalysts [1,2]. The active spices of group 4 single-site catalyst is an ion pair composed of a cationic metal center and a counter anion which are derived from an organometallic procatalyst and a cocatalyst. The catalytic

48

T, Shiano et al.

performance should be therefore strongly dependent on the solvent used for polymerization as well as the procatalyst and the cocatalyst. We have previously investigated the solvent effects in living polymerization of propene with [£-BuNSiMe2Flu]TiMe2 activated by trialkykluminum-free modified methylaluminoxane (dMMAO), which has better solubility in hydrocarbon than dMAO, and found that the syndiospecificity as well as the activity depended on the polarity of the solvent: heptane gave PP with syndiotactic triad (rr) of 0.73, whereas chlorobenzene gave atactic PP [3]. We have recently achieved highly active and highly syndiospecific living polymerization of propene in heptane using [f-BuNSiMe2(3,6-f-Bu2Flu)]TiMe2 (1) by introducing fert-butyl groups at 3,6positions of the fluorenyl ligand of [tBu BuNSiMe2Flu]TiMe2 [4]. In the present work, N we investigated the solvent effects in this Mev. / TJ 6 system, since highly syndiospecific system is Me** \ / % more suitable to investigate the steric defects which are useful as the diagnosis of _^ stereospecific polymerization mechanism. *Bu 1 2. EXPERIMENTAL Materials. All operations were performed under nitrogen gas using standard Schlenk techniques and all solvents were dried by usual procedures and freshly distilled before use. The Ti complex 1 and dMMAO were prepared according to the method reported previously [3]. Research grade propene (Takachiho Chemicals Co.) was purified by passing it through columns of NaOH, P2O5, and molecular sieves 3 A .followed by bubbling it through a NaAlH 2 Et 2 /l,2,3,4,tetrahydronaphthalene solution. Polymerization Procedure. Polymerization was performed in a 100-mL glass reactor equipped with a magnetic stirrer and carried out by the following method. At first, the reactor was charged with prescribed amounts of dMMAO and solvent, i.e., heptane, chlorobenzene or the mixture of heptane and chlorobenzene. After a certain amount of gaseous propene was dissolved in the solution of dMMAO, polymerization was started by the addition of 1 mL solution of 1 (20 /anol) in each solvent. Polymerization was conducted for one hour and terminated with acidic methanol. The polymer obtained was adequately washed with methanol and dried under vacuum at 60 °C for six hours. Analytical Procedure. Molecular weight and molecular weight distribution of polymer obtained were determined by gel permeation chromatography with a Waters ISO CV at 140 °C using o-dichlorobenzene as a solvent. The parameters

9, Effects of Solvents in Living Polymerization ofPropene

49

for universal calibration were K = 7.36 x 10"s, a= 0.75 for polystyrene standard and K = 1.03 x 10"4, a= 0.78 for PP samples. The 13C NMR spectra of PPs were measured at 130 °C on a JEOL GX 500 spectrometer operated at 125.65 MHz in the pulse Fourier-Transform mode. The pulse angle was 45° and about 10 000 scans were accumulated in pulse repetition of 5.0 s. Sample solutions were prepared in l,ls2,2-tetraehloroethane-e4 and the central peak of the solvent (74.47 ppm) was used as an internal reference. Differential scanning calorimetry (DSC) analyses were performed on a Seiko DSC-220. The samples were encapsulated in aluminum pans and annealed at 80 °C for four hours to ensure sufficient time for crystallization. After annealing, the DSC curves of the samples were recorded under a nitrogen atmosphere with a heating rate of 10 °C/min from 20-200 °C. 3. RESULTS AND DISCUSSION J.I. Propene Polymerization in various solvents Propene polymerizations were conducted by 1 activated with dMMAO in heptane, chlorobenzene and the mixture of heptane and chlorobenzene (1:1 in volume) at 0 °C. The results are summarized in Table 1. The polymerizations proceeded quantitatively regardless of the solvent used and gave the polymers with narrow polydispersities. Table 1 Results ofPropene Polymerization with [r-BuNSiMe2(3,6-?-Bu2Flu)]TiMez-dMMAO" entry

solvent15

propene

(e)

a

MJMne

yield 4

{%)

(xlO )

iVd Ounol)

1

0.63

H

100

6.1

1.37

10

2

0.63

H/CB

99

5.6

1.30

11

3

0.63

CB

100

5.8

1.33

11

4

0.63 + 0.638

H

100

11.2

1.29

11

5

0.63 + 0.63 s

H/CB

100

11.6

1.30

11

6

8

CB

100

11.4

1.31

11

0.63 + 0.63

Polymerization conditions: solvent = 30 mL, Ti = 20 ^mol, Al = 4.0 mmol, 0 °C, 1 h. b Solvent: H = heptane, CB = chlorobenzene, H/CB = 1:1 in volume e Number average molecular weight and molecular weight distribution determined by GPC using universal calibration. d Calculated from yield and Mn. e Determined by 13C NMR. f Melting temperature determined by DSC. 8 After the propene polymerization with 0.63 g propene in each solvent for 1 h, 0.63 g of propene was added, and the polymerization was conducted for further 1 h.

50

T. Shmno et al.

To investigate the living nature of the 1-dMMAO system in each solvent, we conducted post-polymerization at 0 °C: the first-step polymerization was conducted under the same conditions of run nos. 1-3, and the second-step polymerization was conducted for another one hour after the addition of the same amount of propene with the first step. The results are shown in Table 1 (run nos. 4-6). The conversions of second step were also quantitative regardless of the solvent used, and the number-average molecular weight (Mn) became almost double of those of the first-step polymers with keeping the number of polymer chains (JV) constant. The N value was also independent of the solvent and about a half of the Ti complex. These results indicate that living polymerization of propene proceeded with 1-dMMAO in heptane, chlorobenzene and the mixture of heptane and ehlorobenzene, and the initiation efficiency was about 50 % irrespective of the solvent used. 3.2. Structures ofpolypropylenes obtained in various solvents The effect of solvent on the structure of PP was investigated by 13CNMR, The spectra obtained in heptane and chlorobenzene did not show any resonance assignable to regio-irregular propene unit, which indicates that the 1-dMMAO system was highly regiospecific irrespective of the solvent used. The steric pentad distributions were then determined from the resonances of methyl carbons, and the results are shown in Table 2. The syndiotactic pentad value (rrrr) was the highest in heptane (0.83) and decreased to 0.28 in heptane/ chlorobenzene mixture and 0.20 in chlorobenzene. Consequently the polymer obtained in heptane showed the melting point at 123 °C, whereas those obtained in chlorobenzene and heptane/chlorobenzene mixture did not show any melting point. Table 2 Steric Pentad Distributions of Polypropylenes Obtained in Various Solvents'1 Entry

Steric pentad content 15

rmrtn

rrrr

0.01

1(H)

0.00

0.00

0.03

0.04

rmrr mmrm 0.03

2 (H/CB)

0.00

0.04

0.03

0.07

0.24

0.12

0.28

0.20

0.02

3(CB)

0.04

0.08

0.05

0.11

0.22

0.11

0.20

0.18

0.04

(solvent )

mmmm mmmr

13

rmmr

mmrr

rnrrr

niton

0.83

0.06

0.00

b

"Determined by C NMR. Solvent: H = heptane, CB = chlorobenzene, H/CB =1:1 in volume.

In the syndiospeeific polymerization of Cs-symmetric proeatalyst, two kinds of stereodefect are present [5]. One is " arising from the "chain

9. Effects of Solvents in Living Polymerization ofPropene

51

migration" without monomer insertion (A in Scheme 1) and the other is " arising from the "selection miss" of the prochiral face of propene at the enantiomorphic site (B in Scheme 1). Table 2 indicates that the rmmr content of 0.03 was almost independent of the solvent used but the rmrr content was drastically increased by the addition of chlorobenzene from 0.03 to 0.24. We can therefore conclude that the low syndiospecifieity in the presence of chlorobenzene is ascribed to the promotion of the "chain migration" but not to the low selectivity of the prochiral face at the enantiomorphic site.

rmrr

I I I

Scheme 1 Two stereoirregular sequences formed in syndiospeciflc polymerization of propene by a C,-synimetric procatalyst

The change of the syndiospecifieity observed by the present Ti complex should be interpreted by the state of the active ion-pair. The dMMAO-polar solvent system gives the solvent separated ion-pair, which allows the growing chain to migrate between the two enantiomeric ligand sites on the Ti cation without monomer insertion. On the other hand, the fixed ligand structure of the Ti complex is independent of the solvent. Consequently the enantioselectivity of the prochiral face unchanged in heptane and in chlorobenzene. The decrease of

52

T. Shiono et al.

the syndiospecifieity in polar solvents was also reported in propene polymerization with Cs~symmetric zirconocene catalysts by several researchers [6-8]. 4. CONCLUSIONS Living polymerization of propene proceeded with [r-BuNSiMe2(3,6-fBu2Flu)]TiMei (1) activated by trialkylaluminum-free MMAO (dMMAO) in heptane as well as chlorobenzene and the heptane/chlorobenzene mixture. The syndiospecificity of the catalysts was however dependent on the solvent used, Syndiotactic crystalline PP was obtained in heptane, whereas amorphous PP was formed in chlorobenzene and the heptane/chlorobenzene mixture. Acknowledgements The authors thank Tosoh-Finechem Co., Ltd. for donating MMAO. T. S. also acknowledges support from the New Energy and Industrial Technology Development Organization (NEDO) under the Ministry of Economy, Trade and Industry (METI), Japan, through grant for the project on "Nanostruetured Polymeric Materials" in the " Material Nanotechnology Program" (2001-). Refereneei [1] W. Kaminsky, Advances in Catalysis 46 (2001) 89-159. [2] V. C. Gibson, and S. K. Spitzmesser, Chem. Rev. 103 (2003) 283-315. [3] K. Nishii, T. Matsumae, E. O. Dare, T. Shiono, and T. Ikeda, Macromol. Chem. Phys. 205 (2004) 363-369. [4] Z. Cai, T. Ikeda, M. Akita, and T. Shiono, Macromolecules 38 (2005) 81358139. [5] J. A. Ewen, M. J. Elder, R. L. Jones, L. Haspeslagh, J. L. Atwood, S. G. Bott, andK. Robinson, Makromol. Chem., Macromol. Symp. 48/49 (1991) 253295. [6] N. Herfert, and G. Fink, Makromol. Chem. 193 (1992) 773-778. [7] M.-C. Chen, and T. J. Marks, J. Am. Chem. Soc. 123 (2001) 11803-11804. [8] V. Busico, R. Cipullo, F. Cutillo, M. Vacatello, and V. V. A. Castelli, Macromolecules 36 (2003) 4258-4261.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

53

10 Preparation of Ethylene/Polyhedral Oligomeric Silsesquioxane(POSS) Copolymers with rflc-Et(Ind)2ZrCl2/MMAO Catalyst System Dong-ho Leea*, Keun-byoung Yoona, Myung-sung Junga, Jin-ki Sungb and SeokKyunNotf "Department of Polymer Science, Kyungpook National University, Daegu 702-701, Korea e-mail; [email protected] b R&D Center, Korea Petrochemical Inc., Ulsan 680-110, Korea "School of Chemical Engineering and Technology, Yeongnam University, Gyeongsan, 712-749, Korea

Abstract To prepare the organic/inorganic hybrid eopolymer, the norbornene derivatives of polyhedral oligomeric silsequioxane(POSS) such as norbomenylethyl-POSS (N-POSS) and dimethyl(norbornenylethyl)silyloxy-POSS(N-Si-POSS) had been copolymerized with ethylene by catalyst system of rae-Et(Ind)2ZrCl2/modIfied methylaluminoxane(MMAO). The catalytic activity decreased with the feed amount of POSS comonomer, and it was found that the reactivity of N-Si-POSS was larger than that of N-POSS. The unreacted POSS monomer was removed completely by washing the copolymerization product with n-hexane. The melting point of eopolymer decreased with POSS content while the thermal stability, especially oxidation stability of eopolymer was improved in a great extent relative to conventional polyethylene.

1. INTRODUCTION In the past decade, the researcher's interest has been widely attracted to the possibility of preparing the hybrid materials and nanocomposites having the

54

D.KLeeetal.

inorganic cage molecules constituted by a silicon-oxygen framework. These molecules, named polyhedral oligomeric silsesquioxane(POSS), were noted by the general formula (RSiOi,s)n where R is hydrogen or an organic group[l]. POSS is surely an attractive material as it can be easily functionalized by chemically altering the R substituent groups, thus having the potentiality of undergoing copolymerization and grafting reactions[2,3]. The presence of the thermally robust POSS moiety was found to drastically modify the polymer thermal properties supplying the greater thermal stabilily to polymer matrix and also allowing the tailoring of polymer glass transition temperature by tuning the POSS concentration^], A very few works have been reported so far as regards the preparation of nanocomposites with polymerizable POSS and olefins[5,6]. In this paper, we report an efficient synthetic route for the preparation of ethylene/POSS copolymers and the enhancements of physical properties of copolymer.

2. EXPERIMENTAL Materials. The a«sa-metallocene of rae-Et(Ind)2ZrCl2(Strem Chemicals, U.S.A.) was purchased and used as received. Modified methylaluminoxane (MMA0-3A: 6,7 wt% Al, Tosoh Finechemical Corp., Japan) was used without further purification. The norbornenylethyl-POSS(N-POSS) and dimethyl(norbomenylethyl)silyloxy-POSS(N-Si-POSS) were purchased from Aldrich and used as received. Ethylene(E, Korea Petrochem. Ind. Co., Korea) was used after passing through the columns of CaSO4 and P2O5, and toluene(Duksan Chemical Co., Korea) was purified after refluxing with sodium-benzophenone complex. Polymerization procedure. All operations were carried out under nitrogen atmosphere. In a 300 ml glass reactor were introduced sequentially the proper amounts of toluene, POSS solution, MMAO solution and then the system was saturated with E, With a continuous flow of E, the polymerization was initiated by injecting the toluene solution of metallocene catalyst and continued for lh. Polymer characterization. The composition of copolymer was analyzed with carbon-13 nuclear magnetic resonance spectroscopy(13C-NMR, Varian, Unity, 300MHz) in bromobenzene-ds at 135 °C. Gel permeation chromatography(GPC, Waters, Alliance GPC/V2000) was performed in trichlorobenzene at 150 °C to measure the molecular weight and molecular weight distribution. The thermal properties of the obtained polymer were measured by means of differential scanning calorimetry(DSC, DuPont TA 2000) at 20 °C/min with 2nd run and thermal gravimetric analysis(TGA, Shimadzu TGA-50) at 10 °C/min.

10. Preparation ofEthylene/POSS Copolymers

55

3. RESULTS AND DISCUSSION 3.1 Copolymerization ofethylene with N-Si-POSS or N-POSS The oraa-metallocene/MAO catalysts systems can be used for copolymerization of ethylene(E) with norbornene(N) to generate cyclic olefin copolymers with N concentration up to 30 mol%[7]. In stead of Ns POSS derivatives of NSi-POSS and N-POSS were used in the E copolymerization initiated with racEt(Ind)2ZrCl2/MMAO catalyst system as summarized in Table 1. Table 1. Copolymerization of E and POSS Comonomer POSS Feed(mol/LxlO j ) Activity* Copolymer PDIC ([E]/[POSS]) (mol%f 1002 33.9 E/N-Si-POSS-1 0.73 6.3 5/0.8 931 22.4 E/N-Si-POSS-2 5/1.6 6.2 1.17 0.22 1944 11.7 E/N-FOSS-1 5/0.8 2.3 E/N-POSS-2 2.1 31 5/1.6 0.37 8.7 PEd 5/2315 10,2 2.8 Polymerization conditions; [Zr]=1.9 xio"s mol/L, [Al]/[Zr]=3000, 50 mL toluene, 1 atm ethylene, reaction time : lh. a Activity in [kg polymer/(mol catalyst-h)], b As determined by 13C NMR. e As determined by GPC. d Reaction time : 15 min.

With the addition of POSS, the catalytic activity decreased. As expected, the POSS content of copolymer increased with feed amount of POSS. The composition of copolymer was obtained from 13C-NMR spectrum of Fig. 1. C H 2, CH

A

-E/N-Si-POSS-1 E /N -S i-P O S S -1 -E/N-POSS-1 E /N -P O S S -1

y

x

H 2C

H 3C R

O S iO Si O

R

OR O Si Si O R

-

O

O

Si Si O R O

Si

CH 2

b, c

CH 3

b b

Si O Si O

a

I' !.

R

R

40

a

C 7cbb

c

O

35

30

I

1

Cyclopentyl group c t g of POSS Of

i 25

20

15

1.13C-NMR spectrum of E/N-Si-POSS-1 copolymers Fig. 1.

7

6

5

4

3

L o g (M w ) Log(MJ

Fig. 2. GPC curves of E/POSS copolymer

At constant feed mole ratio, the POSS content of E/N-Si-POSS copolymer was larger than that of E/N-POSS, which indicated that N-Si-POSS was more reactive than N-POSS in the copolymerization with E. The polydispersity index (PDI) of E/N-Si-POSS copolymer was much higher than that of E/N-POSS copolymer as well as PE homopolymer. In other word,

56

D, H.Lee et al.

the molecular weight distribution of E/N-Si-POSS copolymer was found to be much wider than that of E/N-POSS copolymer as shown in Fig. 2, And the E/N-Si-POSS copolymer exhibited a bimodal GPC curve. It could be speculated that the reason of bimodal distribution might be due to the silyloxy, Si-O- bridge bond of N-Si-POSS comonomer which can give some effects on the formation of catalytic active site. The more detailed study on the bimodal molecular weight distribution of E/N-Si-POSS copolymer is on the progress. 3.2. Purification ofE/POSS copolymer For the exact physical characterization of polymeric material, the purification procedure of polymer product is critical in removal of the unreacted monomers and impurity. Because POSS is soluble in n-hexane, the polymerization mixture obtained by precipitating with methanol was washed with a plenty of n-hexane to remove the unreacted POSS comonomer from E/POSS copolymer. After washing with n-hexane, the solid product was analyzed with GPC as shown in Fig. 3. \ TCB(trichlorobenzene) TCB(trichlorobenzene)

N-Si-POSS

antioxidant

I E/N-Si-POSS-1 copolymer E/N-Si-POSS-1

POSS S/MA-POSS copolymer 0

10

20

30

Retention Time(min) Retention

Fig. 3. GPC chromatograms of E/N-Si-POSS-1 and S/MA-POSS copolymers

For E/N-Si-POSS-1 copolymer after treating with n-hexane, no peak of N-SiPOSS comonomer was observed indicating that unreacted POSS monomer was removed completely by washing with n-hexane. On the other hand, a peak of POSS comonomer residue was observed in the commercial product (Hybrid Plastics, U.S.A.) of styrene(S)/methacrylpropylisobutyl-POSS(MA-POSS) copolymer. No information for the purification method of S/MA-POSS copolymer had been received from Hybrid Plastics after being asked by e-mail.

10, Preparation ofEthylene/POSS Copolymers

57

3.3, Thermal properties of copofymer The melting temperaturefFm) and heat of fusion(^i^) of E/POSS eopolymers was measured by DSC and the results were given in Table 2, Table 2, Thermal Characterization of E/POSS Copolymers AHQIg) Ciystallinityf/o) TJX)

Copolymer E/N-Si-POSS-1 E*4-Si-POSS-2 E*4-POSS-1 E*J-POSS-2 PE

112 106 121 118 131

56 51 112 100 142

19 17 38 34 48

AHf (Heat of fusion of 100 % crystallized PE)=294 J/g [8] A gradual decrease in Tm and AH of the eopolymers was observed with an increase in POSS content (Table 1) of the copolymer, which clearly suggested a random copolymer structure. The degree of erystallinity which was calculated[8] from AR° also declined with the incorporation of POSS comonomer. To examine the thermal stability of E/POSS copolymers, the TGA thermograms of copolymers were obtained under air as well as under nitrogen as shown in Fig. 4.

Under N2

-PE - BN-Si-POSS-1 BN-Si-POSS-2

— PE — - BN-SI-POSS-1 — BN-H-PQSS-2

100

200

300

TempfC)

400

500

800

TempfC)

Fig. 4. TGA thermograms of E/POSS copolymers The thermal stability of copolymer under air was much improved compared to PE. Since PE decomposition in air is through random chain scission to generate free radicals, a cross-linking mechanism around the POSS silicone core was speculated as an explanation for the improved thermal stability[6]. The

58

D, HJLee et al

existence of POSS nanoparticles facilitates recombination of the free radicals and raises stable temperature regime. Another possible explanation for the improvement of thermal oxidative stability is the formation of a silica layer on the surface of the polymer melt in the presence of oxygen, which serves as a barrier preventing further degradation of the underlying polymer.

4. CONCLUSION The ethylene could be copolymerized with norbomenylethyl-POSS(N-POSS) and dimethyl(norbornenylethyl)silyloxy-POSS(N-Si-POSS) by using the ansametallocene of rae-Etflnd^ZrCla catalyst with MMAO cocatalyst The catalyst activity for copolymers decreased with incorporation of POSS comolecules. By washing the copolymerization product with n-hexane, the unreacted POSS comonomer could be removed completely. The melting temperature and heat of fusion of E/POSS eopolymer dramatically decreased with addition of small amount of POSS molecule. By incorporation of POSS, thermal oxidative stability of eopolymer was much improved, especially.

5. Acknowledgements The part of this work was supported by grant (R01-2004-000-10563-0) from the Korea Science and Engineering Foundation.

6. References [1] G. Li, L. Wang, H. Ni, C. U. Pittman Jr., J. Inorg. Organomet. Polym. 11, (2001) 123. [2] F. J. Feher, T. L. Tajima, J. Am. Chem. Soc., 116, (1994) 2145. [3] F. J. Feher, K. J. Weller, J. Chem. Mater., 6, (1994) 7. [4] J. J. Schwab, J. D. Lichtenhan, Appl. Organometal, Chem., 12, (1998) 707. [5] P.T. Mather, H. G. Jeon, A. Romo-Uribe, Macromolecules, 32, (1999) 1194. [6] L. Zheng, R. J. Farris, E. B. Coughlin, Macromolecules, 34, (2001) 8034. [7] D.H. Lee, Y.Y. Choi, J.H. Lee, Y.S. Park, S.S. Woo, e-Polymers, no. 019 (2001) [8] B. W. Wunderlich, "Macromolecular Physics", Vol. 3, p.63, Academic Press, New York, 1980

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

59

11 Norbornene and Ethylene Polymerization with Palladium and Nickel Complexes with Potentially Tri- or Tetradentate Ligands Dong Whan Lee", Cheal Kimb, and Ik-Mo Leea* "Department of Chemistry, Inha University, 253 Yonghyundong, Namku, Incheon, 402751, Korea, e-mail: imlee®,inha. ac. kr b Department of Fine Chemistry, Seoul National University of Technology, Seoul, Korea, e-mail: [email protected]

Abstract New palladium and nickel complexes containing potentially tri- and tetradentate ligands such as functional P-ketoiminates, l,2-bis(pyridine-2carboxamide)benzene derivatives, and 6,6'- bis(alkoxymethyl)-2,2*-bipyridines have been prepared and characterized. These complexes are active towards olefin polymerization on activation with MAO or H(OEt2)2BAr'4 (Ar'= 3,5(CF3)2C6H3). 1. INTRODUCTION Recently, late transition metal complexes, especially palladium and nickel ones, as olefin polymerization catalysts have attracted increased attention due to their less electrophilicity and greater heteroatom tolerance [1]. Up to date, many catalytic systems generally contain bidentate PAO, NAO, PAP, and NAN ligands [2]. cs-Diamine complexes reported by Brookhart [3] and salicylaldiminate ones by Grubbs [4] are the representative systems. However, tri- or higher dentate ligands are generally known to contribute less activity towards olefin polymerization than bidendate ligands [5].

60

D. W. Lee et at

The outcome would be interesting if internal bases, L are connected to the NAO and NAN systems because L should be replaced by incoming olefin monomer during polymerization. In this presentation, we report the olefin polymerization results obtained with late transition metal complexes with potentially tri- or tetradentate ligands. Norbomene and ethylene were effectively polymerized with new nickel and palladium complexes containing potentially tri- or tetradentate ligands in the presence of niethylaluminoxane (MAO) or borate cocatalysts. Tri- or tetradentate ligands used in this study include functional fj-ketoiminates, 1,2bis(pyridine-2-carboxamide)benzene derivatives, and 6,6'- bis(alkoxymethyl)2,2'-bipyridines. 2. EXPERIMENTAL All the works involving moisture-sensitive compounds were carried out using standard Schlenk or dry-box techniques. All reagents, purchased from Aldrich Chemical Co., were used as supplied commercially without further purification. 'H and 13C NMR spectra were recorded by using 5 mm tube on a Varian Unity Inova 400 (400.265 and 100.657 MHz, respectively) or Varian Gemini 2000 (199.976 and 50.289 MHz, respectively) spectrometer and were referenced to tetramethylsilane (TMS). 31P NMR spectra were recorded on a Varian (162.027 MHz) FT-NMR spectrometer and were referenced to 85% H3PO4. All manipulations were conducted under an inert atmosphere. Elemental analyses were performed with EA-1110 (CE Instruments) in the Inha University. New ligands and complexes are prepared from the reactions described in schemes by using appropriate precursor complexes reported in the literature. H(OEtz)zBAr'4 (Ar'= 3,5-(CF3)2CsH3) [6] has been prepared according to literature procedures. MMAO (Tosoh Finechem Co., 5.7% Al content in toluene) was used as supplied. Homopolymerization of Norbomene with MMAO In an inert (N2) atmosphere, appropriate amount of MMAO were placed into a small vial. To this was added approximately 5mL of solvent, and the mixture gently shaken to dissolve the solids. This stock solution was then added to O.OOSg of catalyst, predetermined equivalents of norbomene dissolved in approximately lOmL of solvent in a 20mL vial containing a stirring bar. The solution was stirred rapidly for predetermined time. The product was quenched by adding acidified methanol. The solid was washed in methanol and dried under vacuum. Homopolymerization of ethylene with MMAO In an inert (N2) atmosphere, appropriate amount of MMAO were placed into a small vial. To this was added approximately 5 mL of toluene, and the mixture gently shaken to dissolve the solids. This stock solution was then added to

11. Norbomene and Ethylene Polymerization with Pd and Ni Complexes

61

O.OOSg of catalyst dissolved in approximately 30mL of toluene in a glass-lined autoclave with a stirring bar. Ethylene was charged at 10 bar in an autoclave. The solution was stirred rapidly for about 10 min. Polymerization was quenched by adding acidified methanol. The solid was washed in methanol and dried under vacuum 3. RESULTS AND DISCUSSION

3.1. Pd complexes with functional $ -ketoiminates Most of the functional P-ketoimines used in this study have been prepared by condensation reactions between corresponding (3-diketones and amines described in the literature with moderate to good yields. However, some of them were synthesized via TMS intermediates and lower yields were generally observed due to multistep reactions. Three kinds of Pd complexes have been prepared and tested for olefin polymerization. These complexes have been synthesized by the following methods (Scheme 1 and 2). These complexes have been characterized with 1H, 13C, and 31P NMR, Elemental analysis, and X-ray crystallography. From the structures of palladium complexes determined by X-ray crystallography, it is found that internal bases are coordinated to the metal only in [Pd(Me)(p-ketoiminate)] as we have designed. These complexes were found to be active for norbomene and ethylene polymerization on activation with [H(EtaO)2]+BAr4>" (Ar'=3,5bistrifluoromethylphenyl) or MAO. NMR studies showed that allyl or f$ketoiminate ligands are dissociated to open a site for incoming olefin monomer in the [Pd(allyl)(P-ketoiminate)] complexes and addition of H+ onto the pketoiminate was occurred first on addition of [HfEtaOy^BAr^''. However, these complexes are not active without cocatalysts. Selected results are summarized in Table 1, 2 and 3. MMAO is more efficient for the activation for polymerization. Generally, the polymerization activity increases with the following order; [Pd(allyl)(p-ketoiminate)] < [Pd(Me)(PPh3)(p-ketoiminate)] < [Pd(Me)(P-ketoiminate)].

D. W. Lee et al.

62 1 hr

+ T1(OC 2 H 5 ) O

ether, RT

N,

2hr

ether, below -20°C

la R=Me, Rl= (CH2)jOMe 2a R=Me, Rl= (CH2)2OMe 3a R=Me, Rl = CH(Me)CH2OMe 4a R=Me, Rl= 2-methoxybenzyI Sa R=Me, Rl= 2-m ethoxy-6-m ethylphenyl 6a R=Me, Rl= 2-(CH2)2py 7a R=Ph, Rl= (CH2)3OMe 8a R=Ph, Rl= 9a R=Ph, Rl= CH(Me)CH2OMe 10a R=Ph, Rl = 2-methoxybenzyl l l a R=Ph, Rl = 2-m ethoxy-6-m ethylphenyl 12a R=Ph, Rl = 2-{CH2)2py 13a R=C l= (CH2)3OMe Scheme 1

O.

THF, below -20°C Tl'

Pd(PhCH2NH2)2MeCl THF, below -20BC Me

Scheme 2

* Me

lb R=Me, Rl=(CH2)3OMe 4bR=Me, Rl=2-methoxybenzyl 6bR=Me,Rl=2-(CH2)2py 12b R=Ph, Rl=2-(

6e R=Me, 12c R= 14c R=Me ISc R=

11. Norbornene and Ethylene Polymerization with PdandNi Complexes

63

Table 1 Results of Norbomene Polymerization with a Cocatalyst, catalyst

solvent

yield

Activity

(%)

(kg/Pdmol

CH2C12

95

263

PhCl

77

204

PhMe

13.5

21,3

CH2C12

35

191

PhCl

60

328

PhMe

25

138

fib

CH2C12

45.2

295

12b

CH2C12

57.5

456

PhCl

94.6

749

PhMe

14.1

112

6c

CH2C12

84.5

477

1

CH2CI2

62.7

355

2

CH2C12

16.5

93

12c

CH2C12

67.2

531

PhCl

48.8

379

PhMe

40.7

318

14c

CH2C12

79.4

1026

15c

CH2C12

86.6

657

16

CH2CI2

90.7

329

PhCl

97.3

348

PhMe

62.9

224

[Pd(methallyl)Cl]2

6»

6c

6c

hr)

Reaction temperature: 25°C, solvent volume = 15ml, [monomer]/[catalyst] = 1000, reaction time = 5min, 14c = 3min,': [cocatalyst]/[catalyst] = 4, 2: [eoeatalyst]/[catalyst] = 10

D, W. Lee et at.

64

Table 2 Results of Norbornene Polymerization with a Cooatalyst, MMAO catalyst

solvent

yield

Activity

(%)

(kg/Pd-mol/hr)

6b

CH2C12

1.90

24600

12b

CH2C12

1.95

26100

PhCl

1.90

22000

PhMe

0.83

5030

6c

CH2C12

1.88

37100

12c

CH2C12

1.82

51400

PhCl

1.88

53000

PhMe

1.31

34800

14c

CH2C12

1.95

93400

15c

CH2C12

1.90

77100

16

CH2C12

2.0

28300

PhCl

1.85

20500

PhMe

0.96

6200

Reaction temperature: 25 "C, solvent volume =15 ml, Al/Pd = 1000, b and c type catalysts: 1000 equivalents norbomenes, reaction time = 2 min, 14c reaction time: 1 min.

Table 3 Results of Ethylene Polymerization with Cocatalyst, MMAO yield

Activity

(%)

(kg/Pd-mol/hr)

fib

1.35

1620

12b

1.40

1810

6c

0.12

162

12c

0.41

675

14c

0.09

98

16

0.61

714

catalyst

Reaction temperature: 25 °C, toluene volume = 35 ml, Al/Pd = 1000, ethylene pressure =10 bar, reaction time =10 min.

11. Norbomene and Ethylene Polymerization with Pd and Ni Complexes

3,2. Ni complexes derivatives

with

65

lt2-bis(pyridine-2-carhaxamide)benzeme

X,

1 : X, = H 2 : X, = H 3 : X, = Cl 4:X., = H S : X., = H 8 : X, = CH 3 7 : Xi = H

X 2 = N 0 2 (H2bpn) X2 = F (H2bpf) (H2bpc) X 2 = Cl Xa=H (H2bpb) X a = CH 3 (HaMebpb) X 2 = CH a {l-^M^bpb} X a = OCH3(HaMBObpb)

8 ; X, = H S: X, = H 10 : X! = Cl 11:X, = H 12 : X, = H 13 : X, = CH a 1 4 : Xi = H

X2 = N 0 2 X2 = F X 2 = Cl X2 = H X 2 = CH 3 X 2 = CH 3 X a = OCH 3

Scheme 3

These complexes were prepared by the reaction described in Scheme 3 and activated with MAO to produce polynorbornene and polyethylene. Selected polymerization results are summarized in Table 4. The polymerization mechanism by these complexes is interesting because there are no vacant site for incoming olefin and no alkyl or halide ligands for the insertion of coordinated olefins. One terminal pyridine may dissociate first by the reaction with acidic MAO to leave a vacant site and transfer of alkyl group from Al to Ni may follow to give a site for incoming olefin. Therefore, simple Lewis acids such as trialkylaluminums are expected to catalyze polymerization even though activities are not as high as MAO. However, addition of 400 equivalents of AlMe3 or Al(i-Bu)3 instead of MAO did not induce polymerization at all even after 24 hrs. This may be due to preferential coordination of dissociated imido anion and Lewis acidities of AlMe3 or Al(i-Bu)3 may not be enough to prevent this reaction. Dried MMAO also did not induce polymerization while dried MAO induced less and slower polymerization than normal MAO (MAO with free AlMe3). Probably only MAO species with more acidity guarantees a vacant site for the incoming olefin by preferential combination with the dissociated imido ligand. Higher activity in polar solvent can be interpreted by stabilization of the charged intermediate.

D. W. Lee et al.

66

Table 4 Results of Norbomene Polymerization with New Nickel Complexes catalyst

8

9

10

11

12

13

solvent

yield

Activity

Mw

MJMn

5

CO

(%)

(kg/Pd-mol/hr)

(xlO )

25

0.30

845

6.18

1.99

50

0.55

1549

5.89

2.20

PhCl

25

0.60

1703

13.8

2.44

PhMe

25

0.39

1106

5.73

2.18

PhCl

25

0.85

2160

11.2

2.83

PhMe

25

0.24

701

2.99

1.93

PhCl

25

0.31

854

8.14

2.19

PhMe

25

0.10

214

1.89

1.99

PhCl

25

0.26

736

4.21

2.11

PhMe

25

0.23

639

4.82

2.03

PhCl

25

0.28

805

10.03

2.32

PhMe

25

0.35

993

3.36

2.01

PhMe

50

0.46

1304

1.70

1.97

70

0.62

1758

1.18

1.99

100

0.53

1315

0.73

1.95

25

0.36

1018

9.66

1.95

50

1.20

1697

7.19

2.17

70

1.53

2164

3.94

2.79

100

1.24

1754

1.62

4.29

PhMe

25

0.49

1390

8.67

1.81

PhCl

25

0.59

1673

9.46

1.98

PhCl

14

T

Reaction temperature: 25 °C, solvent volume = 15 ml, Al/Pd =100,1000 equivalents norbomenes, reaction time = 10 min, Ni = 2.4 (imol.

11. Norbomene andEthylene Polymerization with PdandNi Complexes

3.3. Pd and bipyridines

NiCj,

Ni

complexes

with

6,6*-

67

bis(alkoxymethyl)-2,2'-

+

R=Et(l),i-Pr(2),Cy(3),Ph(4) THF Pd(CH3CN)2Cl reflux

OR

OR

R = Et(5) ! i-Pr(6) ! Cy(7),Ph(8) Scheme 4. Synthesis of the complexes with 6,6*-bis(alkoxymethyl)-2s2*-bipyridines.

Ni and Pd complexes have been prepared by the reactions described in Scheme 4. Since these Ni complexes show paramagnetic properties, they are characterized by elemental analysis and X-ray crystallography. Selected norbomene polymerization results on activation with MMAO are summarized in Figure 1. Pd complexes showed marked increase in activity with the introduction of internal bases, especially OEt but slight increase in activity is observed in the cases of Ni catalysts. i d 5C0 -

— 100 -

/

\

I >

o Activity (t

T

/

"

^

\

B'-—~~~

u OEt

opr

ligands of catalysts

.

ocy

Figure 1. The Effects of substituents on the catalytic activity towards norbomene polymerization: catalyst: 0.23 x 10"3 mmol(Ni), 0.23 x 10"3 mmol(Pd), solvent: chlorobenzene 15ml, reaction time : 2 min, monomer: 2 g ([monomer]/[cat.]=l 0,000 (Ni), 100,000 (Pd)), reaction temp.: R T , M M A O : 1,000 e q .

68

D. W.Leeetal

4. CONCLUSIONS In conclusion, we have shown that Ni and Pd complexes with potentially tri- or tetradentate ligands could be active catalysts towards olefin polymerization and catalytic activity could be improved by simple introduction of internal bases. Acknowledgements Authors are grateful for the financial support from Samsung Atoflna Co., Korea Science and Engineering Foundation (KOSEF) (R01-2002-000-00146-0) and I.M. Lee shows his gratitude to both Inha and Hiroshima universities for allowing the sabbatical leave (2004, 9 - 2005. 2). Lee also appreciates the invitational fellowship hosted by Professor T. Shiono of Hiroshima University and supported by Korea Science and Engineering Funds (KOSEF) and Japan Society for the Promotion of Science (JSPS) (2004). References [1] (a) S. D. Ittel, J. K. Johnson, M. Brookhart, Chem. Rev. 100 (2000) 1169. (b) S. Mecking, Angew. Chem. Int. Ed. 40 (2001) 534. [2] G. J. P Britovsek,. V. C. Gibson, D. F. Wass, Angew. Chem. Int. Ed. 38 (1999) 428. [3] L. H. Schultz, D. J. Tempel, M. Brookhart, J. Am. Chem. Soc. 123 (2001) 11539. [4] T. R. Younkin, E. F. Connor, J. I. Henderson, S. Friedrich, R. H. Grubbs, D. A. Bansleben, Science 287 (2000) 460. [5] (a) N. A. H. Male, M. Thornton-Pett, M. Bochmann, J. Chem. Soc, Dalton Trans. (1997) 2487. (b) T. M. Kooistra, K. F. W. Hekking, Q. Knijnenburg, B. de Bruin, P. H. M. Budzelaar, R. de Gelder, J.M.M. Smite, A. W. Gal, Eur. J. Inorg. Chem. (2003) 648. [6] M. Brookhart, B. Grant, A. F. Volpe Jr., Organometallies 11 (1992) 3920.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

69

12 Effects of Bridge Nature of Dinuclear HalfTitanocenes on Polymerization Properties Seok Kyun Noha*, Yong Rok Leea, Won Seok Lyoob, Dong-Ho Leec "School of Chemical Engineering and Technology, Yeungnam University, 214-1 Daedong, Oyeongsan, 712-749, Korea, bSchool of Textiles, Yeungnam University, 214-1 Daedong, Gyeongsan, 712-749, Korea cDepartment of Polymer Science, Kyungpook National University, Daegu, 702-701, Korea

Abstract A series of dinuelear half-titanoeenes with polymethylene and xylene as a bridge between two eyelopentadienyls have been synthesized and polymerization behavior of these complexes has been exploited. It was found that the activity of the dinuclear half-titanocene showed a clear tendency according to the bridge length, bridge structure, and substituent group at titanium metal. The presence of not only long methylene units but also xylene unit between two active sites contributed significantly to increase the activity of dinuclear half-titanoeenes. Aryloxy substitution at titanium caused to facilitate the polymerization activity. On the other hand arylamine substitution at titanium exhibited a positive impact on thermal stability of the catalyst. It has been found that presence of xylene bridge is clearly effective to produce syndiotactic polystyrene (SPS) with high crystallinity but low molecular weight. All the results indicate the implication that not only the electronic factor but also the steric factor caused by the bridge nature of the dinuclear half-titanocene exerts considerably an influence on the polymerization behavior of the catalysts. 1. INTRODUCTION In 1988 CpTiCla was found to be the first half-metallocene as a catalyst for the production of syndiotactic polystyrene (SPS) by Ishihara and coworkers [1]. Since then plenty of studies have been pursued to make the relation between the

70

S.KNohetal.

properties of the generated polymers and the structural characteristics of the catalysts [2-4]. Recently Nomura have reported polymerization properties of a variety of half-titanoeenes containing different substituent at titanium extensively [5-7], A variety of dinuclear half-metallocene compounds, which contain two mechanically linked metallocene units, have been prepared to examine their catalytic properties [8]. The initial attempt to exploit dinuclear half-titanocene was performed by Royo although he did not pay attention to the styrene polymerization study [9,10]. Flores and coworkers described the synthesis of the dinuclear half-titanocenes with indenyl as a Cp derivative and ethylene as a bridge and study of the effects on activity and syndiospecificity resulting from possible cooperative chemical behavior between two active centers [11]. It turned out that the activity for the dinuclear half-titanocenes is one order of magnitude lower than that for the mononuclear half-titanocene. On the contrary the syndiospecificity of dinuclear half-titanocenes is comparable to the corresponding mononuclear catalyst. An extensive polymerization study with the dinuclear half-titanocene has been probed by our group in recent years [12-15]. In the same manner that we have investigated the dinuclear Kaminsky-type and constrained geometry catalysts a series of the dimielear half-titanocene with polysiloxane and polymethylene bridging ligands have been formed to conduct styrene polymerization. According to the polymerization results some noticeable points have been revealed to display the effects of bridge structure on catalyst properties [16]. In this report we would like to focus on styrene polymerization behaviors of the dinuclear half-titanocenes with the emphasis on the nature of bridging ligand in terms of catalytic activity and syndiotacticity of the formed polystyrene. 2. RESULTS AND DISCUSSION Dinuclear half-titanocene as well as mononuclear half-titanocene is wellknown as an excellent catalyst for the preparation of syndiotactic styrene (SPS) when activated with methylaluminoxane (MAO). In order to investigate the catalytic behaviors of the dinuclear half-titanocene a series of six catalysts have been designed and synthesized to probe the effects of the types and length of bridging ligands, and substituent at titanium metal on the catalytic properties (Scheme 1 and Table 1). These were delivered for the polymerization of styrene in the presence of MMAO ([Al]/[Ti] ratio of 2,000 and 4,000). A variety of styrene polymerization runs have been carried out depending on the reaction conditions and the results are shown in Tables 2 and 3.

12. Effects of Bridge Nature ofDinuclear Half-Titanocenes

71

2.1. Bridging tigand effect The catalytic activities with six dinuclear half-titanocenes exhibited a definite and consistent tendency to understand the influence of the bridge between two titanium centers. It was found that the dinuclear catalyst with more [CH2] units as a bridge represented greater activity. The activity of the catalyst 3 with nine [CH2] was about 25% higher than the catalyst 2 with six [CH2]. On the other hand the molecular weight (Mw) of the formed polymer exhibited the reverse tendency. Mw of SPS prepared by the catalyst 2 was about 20% larger than that of SPS by the catalyst 3. Actually this sort of tendency is very well in accord with the past research outcomes. ""ic\

ci Table 1. Synthesized catalysts Catalyst

B in Scheme 1

Scheme 1 R in Scheme 1

2)6-

2}6-

"(CH2)9-

Cl

—O

—o Cl

H5C

^^%

//

—o

72

S.KNohetal.

Table 2. Results of styrene polymerization using dinuclear half-titanocene with polymethylene bridge [Al]/[Ti]

Catalyst

A

Tm

b

(°C)

Mw

SIC

MJM 4

(x lO" )

fC)

25

2,000

49.3

270.8

95.3

23.1

2.1

40

2,000

51.8

268.4

91.4

15.0

1.7

25

2,000

55.4

269.3

97.0

21.4

2.1

40

2,000

80.7

268.3

97.1

14.3

2.4

25

2,000

57.3

267.9

93.9

17.7

1.9

40

2,000

102.4

267.4

94.4

14.0

2.3

40

4,000

148.1

268.7

94.6

14.7

1.9

1

2

Polymerization conditions: [Ti] = 0.83 x 10-6 mol/1, [St] = 1.32 mol/1 Tp e = Polymerization temperature. A b =Activity (kg-polymer/mol-Ti/h). SIC= Syndiotactic Index

Table 3. Results of styrene polymerization using dinuclear half-titanocene with xylene bridge A"

F ra fC)

SIC

M w (xl0-*)

MJM»

25

65

270.8

95.3

23.1

2.1

40

128

268.4

91.4

15.0

1.7

25

87

269.4

90.2

11.5

2.6

40

277

268.3

91.3

11.4

2.1

25

108

269.3

91.1

13.2

2.3

40

458

267.2

97.4

10.9

2.4

70

169

257.5

93.3

3.8

3.0

25

24

266.7

93.8

19.1

1.7

40

84

266.6

94.3

10.7

2.0

70

361

260.0

90.2

3.1

2.3

Catalyst

1

4

5

6

Polymerization conditions: [Ti] = 0.83 x W mol/1, [St] = 1.32 mol/1, [Al]/[Ti]=2,000. Tp e = Polymerization temperature. A = Activity (kg-polymer/mol-Ti/h). SIe= Syndiotactic Index

12. Effects of Bridge Nature ofDinuclear Half-Titanacenes

73

The most important feature concerned with the bridge effect was the manifested difference between polymethylene and xylene bridge (Table 3). The big activity difference between the catalyst 1 and 4 is able to be attributed to the nature of the bridge from 6 methylenes and xylene, respectively. At 40 °C the activity of the catalyst 4 (277 kg-polymer/mol-Ti/h) with xylene joint was more than twice that of the catalyst 1 (128 kg-polymer/mol-Ti/h) with polymethylene one. Furthermore, the molecular mass difference of the generated SPS by the catalyst 1 and 4 seemed even more phenomenal as shown in Table 3. In fact the highly active catalyst 4 gave rise to the formation of polymers having a significantly shorter length. We would like to relate electronic and steric influences of the catalysts in terms of the bridge nature to these consequences. Electronic influence toward the metallocene is based on the general knowledge that increasing electron density at the active center will draw a stability of the active site, which is a 14electron cationic species in nature, not only to lead high activity but also to produce polymer with high molecular weight [8,16]. Similarly steric influence of the more congested active center will depreciate the activity of the catalyst due to the delay of the rate of monomer coordination. In our experiments the greater activity by the catalyst 3 of more methylene unit as a bridge comparing to the catalyst 2 can be interpreted by either electron donating character of polymethylene linkage or steric disturbance difference due to the dissimilar polymethylene length. The more electron delivered by the adoption of longer polymethylene group as a link between two half-titanocene is able to stabilize the electron deficient active site to speed up the polymerization rate. Suppression of interaction opportunity between two active sites can be speculated to explain an increased activity of the catalyst with more methylene linkage. The different polymerization behavior represented by the xylene-bridged catalyst from the polymethylene-bridged one may also be rationalized by the electronic as well as steric effect. The most distinctive feature between xylene and hexamethylene bridge should be the rigidity of xylene bridge. Xylene linkage is too stiff to arise any kind of intramolecular interaction between two metal centers. On the contrary hexamethylene is flexible enough to draw two active centers close together to make a contact each other. This interaction initiated by the flexibility of the bridge is able to provide an opportunity to transfer electronic information of the active center from one side to the other. It is not unreasonable that steric interaction prevents a facile access of monomer to the coordination site to lead to slowing down the propagation rate. On this basis, it is not so surprising to anticipate that the dinuclear half-titanocene with a flexible, hexamethylene bridge experiences more steric disturbance than the

74

S.K.Nohetal.

one with a rigid, xylene bridge. If this is the occasion, the catalyst 1 should display lower activity comparing to the catalyst 4. As for the rigidity effect on molecular weight of SPS, it can be proposed that the presence of a stiff property of xylene bridge between two active sites can avoid steric hindrance to lead a facile B-H transfer to the titanium and thus makes chain termination easy. The molecular weights of SPS obtained by the catalysts 1-6 are reasonably well correlated with the proposal. The dinuclear half-titanocenes 1-3 holding hexamethylene bridge result in the formation of SPS with higher molecular weight due to the existence of steric interaction between two sites. However, the catalysts 4-6 holding xylene linkage imposing high rigidity to the catalyst produce the shorter polymer chains. 2.2. Substitution effect at titanium It turned out that polymerization behavior of dinuclear half-titanocenes can be considerably affected by changing the substituent at titanium center. For instance, styrene polymerization activity of the catalyst 2 with aryloxy group at titanium was 80.7 kg-polymer/mol/Ti/h, while that of the corresponding dinuclear CGC with chloride was 51.8 kg-polymer/-Ti/h. Likewise the substitution pattern change of the xylene bridged dinuclear half-titanocene resulted in activity change. The catalyst 5 prepared from the catalyst 4 by the aryloxy substitution led to the activity increase from 277 kg-polymer/mol-Ti/h. to 458 kg-polymer/mol-Ti/h. On the other side, arylamine substitution at titanium of the catalyst 4 to make the catalyst 6 gave rise to the sharp decrease of the catalytic activity down to 84 kg-polymer/mol-Ti/h at 40 °C. This result must be come from the substituent influence at titanium center. Interestingly and surprisingly as well, it was found that substitution of arylamine at the metal center delivered significant thermal stability improvement to the dinuclear halftitanicene. At 70 °C activity of the catalyst S was cut to 169 kg-polymer/molTi/h, which was corresponded to only 36% activity value of the activity at 40 °C. This outcome clearly demonstrates that thermal stability of the catalyst 5 with aryloxy at titanium is deteriorated drastically at this temperature. On the contrary, the tendency of the activity variation of the catalyst 6 with arylamine at titanium at the same temperature was shifted to the opposite direction for that of the catalyst 5. Activity of the catalyst 6 at 70 °C was turned out to be 361 kg-polymer/mol-Ti/h which was in fact more than four times larger value comparing with that of the catalyst 5. It was found that all the catalysts except the catalyst 6 exhibited maximum polymerization activity around 40 °C, which decreased with changes of temperature both above and below this temperature. However, the catalyst 6 with amine group at titanium displayed to keep up the tendency of activity increase even at 70 °C. This is

12. Effects of Bridge Nature of Dinuclear Half-Titanocenes

75

actually remarkably distinguished from the previous report by Nomura [7]. According to his results the activity of half-titanocene with arylamme-titanium bond was very sensitive to the polymerization temperature due to the assumed thermal decomposition. We are going to explore temperature sensitivity of the dinuclear half-titanocenes continuously in terms of substituent at metal center. It is noteworthy that the syndiotacticity of the generated polystyrene at this condition maintained above 90% with the sharply reduced molecular weight. These findings may imply some very important points for the preparation of SPS. It is generally recognized that control of both stereoregularity and molecular weight is not trivial at all in polymer synthesis. We think the above observation can be conveniently applied to give rise to the formation of SPS with the controlled molecular weight by use of substitution variation at metal center. Concerning the effect of nitrogen substitution at titanium center on thermal stability of the metallocene, it is known that CGC (constrained geometry catalyst) constituted by the nitrogen-titanium bond along with Cptitanium bond is one of the most stable catalysts thermally. The reason of thermal resist on CGC can be responsible for the presence of nitrogen-titanium bond. It is likely that the strengthening of thermal stability of the catalyst 6 can be attributed to the substitution of arylamine at titanium. 3. SUMMARY A family of the polymethylene and xylene bridged dinuclear half-titanocene have been employed to examine the effect of the structural parameter of these catalysts on the polymerization properties. It turned out that dinuclear halftitanocenes showed reasonable catalytic activity for SPS production according to the characteristics of the catalyst. One of the most important features is that the switch of hexamethylene bridge to xylene bridge between two active centers leads to not only the improvement of polymerization activity but also the reduction of molecular weight of the formed SPS. This outcome can be interpreted by either an electronic or steric effect on catalytic properties. Authors' understanding supports the difference of the steric circumstances between two bridges is a pronounced factor to explain these experimental results. It is noteworthy that the introduction of arylamine instead of chloride or aryloxy group at titanium reinforced the thermal stability of the dinuclear halftitanocene. This can be illustrated clearly by the activity comparison of the catalyst 6 with the other catalysts. Only the catalyst 6 exhibited a higher activity at 70 °C than at 40 °C. Strengthening of thermal property of the catalyst 6 is attributed to the presence of nitrogen-titanium bond likewise the case of CGC. From this study the authors are positive that control of the bridge nature as well as the substitution pattern of the dinuclear half-titanocene is able to be useful to tune the characteristics of the catalyst finely to prepare the desired polymers.

76

S.KNohetal.

Acknowledgements We are grateful to the Regional Technology Innovation Program of the Ministry of Commerce, Industry, and Energy (RT 104-01-04). References [1] N. Ishihara, M. Kuramoto, M. Uoi, Macromolecules 21 (1988) 3356. [2] G. G. Hlatky, Chem. Rev. 100 (2000) 1347. [3] G. J. P. Britovsek, V. C. Gibson, D. F. Wass, Angew. Chem. Int. Ed. Engl. 38 (1999)428. [4] W. Kaminsky, J. Polym. Sci.5 Part A : Polym. Chem. 42 (2004) 3911. [5] W. Wang, M. Fujiki, K. Nomura, J. Am. Chem. Soc. 127 (2005) 4582. [6] K. Nomura, K. Itagaki, Macromolecules 38 (2005) 8121. [7] K. Nomura, K. Fujii, Macromolecules 36 (2003) 2633. [8] S. K. Noh, D. H. Lee, Korea Polymer Journal 9(2) (2001) 71. [9] T. Cuenca, J, C, Flares, R. Gomez, P. Gomez-salt, M.Parra-Hake, P. Royo, Inorg. Chem. 32 (1993) 3608. [10] S. Ciruelos, T. Cuenca, J, C. Flores, R. Gomez, P. Gomez-sal, P. Royo, Organometallics 12 (1993) 944. [11] J. C. Flores, T. E. Ready, J. C. W. Chien, M. D. Rausch, J. Organomet. Chem. 562(1998)11. [12] S. K. Noh, W, S. Jung, K. E. Shin, W. S. Lyoo, D, H. Lee, Polymer Preprints (2005)765. [13] S. K. Noh, M. Lee, D. H. Kim, K. Kim, W. S. Lyoo, D. H. Lee, J. Polym. ScL, Part A : Polym. Chem. 42 (2004) 1712. [14] S. K. Noh, S. H. Kim, Y. Yang, W. S. Lyoo, D. H. Lee, European Polym. J. 40 (2004) 227. [15] T. Tae, S. H. Kim, T. Kim, D. H. Lee, Polymer(Karea), 24(2) (2000) 159. [16] S. K. Noh, S. Kim, J. Kim, D. H. Lee, K. B. Yoon, H. B. Lee, S. W. Lee, W. S. Huh, J. Polym. ScL, Part A : Polym. Chem. 35 (1997) 3717.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

77

13 Modification of Catalytic Properties of Homogeneous Metallocene Catalytic Systems in Propylene Polymerization under Action of Triisobutylaluminum and Lewis Bases N.M. Bravaya*, E.E. Faingol'd, E.A. Sanginov, A.N. Panin, O.N. Babkina, S.L. Saratovskikh, O.N. Chukanova, A.G. Ryabenko, E.N. Ushakov Institute of Problems of Chemical Physics, Russian Academy of Sciences, 142432 Chernogolovka Moscow Region, pr, akademika Sememova 5, Russia e-mail: [email protected]

Abstract Experimental results showing the unique possibilities of modification of catalytic properties of homogeneous metallocene IVB Group catalysts in propylene polymerization under the action of triisobutylaluminum (TIBA) or in the presence of small additives of Lewis bases (LB) are presented. It has been shown that the preactivation of zirconocene dichlorides at low MAO excess (~10z mol/mol) followed by the activation with TIBA also at low molar TIBA excess to over metallocene (-10 2 mol/mol) gives rise to very active homogeneous catalysts for olefin polymerization. The approach allows a 10100-fold decrease of MAO charges. Monomethylated zirconocene complexes with MAO as catalytic intermediates formed under preactivation conditions and the mixture of tetraisobutylalumoxane/polyisobutylalumoxane as cocatalysts formed at nearby stoichiometric amounts of TIBA and MAO were recognized as the key components of the analyzed catalytic systems. It has been shown for the first time that purposeful introduction of almost stoichiometric amounts of ternary amines to the L2MMe2/Ph3CB(C6Fs)4/TIBA catalytic systems (L2MMe2 = Ph2CCpFluMMe2 (M=Zr, Hf), mcMeiSilndiZrMea) can result in an extremely high increase in the catalyst activity, the effect being most pronounced for hafhoeenes in the presence of

78

N ,M, Bravaya et al.

NPh3. It was also shown that TTBA in these catalytic systems acts as the reagent reducing stereoselectivity of the catalyst leading to the formation of stereoblock polypropylenes for Cs-symmetry catalysts. The reasons for the effects observed are discussed. 1. INTRODUCTION One can find in literature a lot of examples of the active role of triisabutylaluminum (TIBA) in metalloeene-based catalytic systems. Being a poor activator for the most part of metalloeenes, it can effectively activate dimethylated 2-substituted bisindenylzirconocenes in ethylene and propylene polymerization [1,2]. Highly active catalytic systems for ethylene and propylene polymerization were obtained by using TIBA as the third component for several zirconocene dichlorides with Ph3CB(C6F5)4 (TB) [e.g., 3-5]. Partial replacement of MAO by TIBA is also used for modification of catalytic properties of homogeneous L2MCI2/MAO systems [e.g., 6-10] leading, under certain conditions, to enhanced catalyst activity, higher incorporation of comonomer, increased catalyst stability, solubility of the catalytic system in aliphatic solvents, etc. Nevertheless, in all listed examples, A1MAO/M molar ratios are sufficient for precatalyst activation without TIBA. There are some other examples of combined MAO/TIBA activation of L2MCI2 when MAO is used for catalyst preactivation at AIMAQ/M molar ratios about order of magnitude lower than those necessary for activation, and only introduction of TIBA makes the system active [11-13]. Therefore, it was of interest to find optimal conditions for metallocene activation in the latter systems, and to reveal catalytic intermediates, as well as to understand the role of TTBA. Analysis of reaction products of Ph2CCpFluZrCl2 (1) and rac-Me2Si(2-Me,4-PhInd)2ZrCl2 (2) with MAO under conditions of preactivation, those of MAO with TIBA, as well as the data on propylene polymerization under the activation of the catalysts with MAO/TIBA, will be presented in the first part of the paper. Highly electrophilic cationic metal-alkyl metallocene complexes of IVB Group, active species of olefm polymerization, are extremely sensitive to the action of nucleophilie substrates due to temporary or irreversible deactivation. However, one can find in literature the examples of the non-deactivating action of donor-like moieties causing either increase in the catalyst activity or changing the molecular-weight and microstructure characteristics of polymers formed [14-17]. Even rather strong Lewis bases (LB) do not necessarily lead to cationic complex decomposition being introduced to a reaction medium [18,19]. In the second part of the paper, exemplifying the catalytic systems L2MMe2/TB/TIBA (L2MMe2=racMe2SiInd2ZrMe2 (3Me) and Ph2CCpFluMMe2 (M=Zr (lMe), Hf (4Me)), we would like to demonstrate that simple introduction of NPhj in a reaction medium can lead to a very high increase in

13, Modification of Homogeneous Metallocene Catalysts

79

the catalyst activity. The effect is most pronounced for hafhocenes. The effect of TIBA decreasing stereoselectivity of 4Me/TB/TlBA system accompanied by the formation of stereoblock syndio/atactic polypropylene will be demonstrated. 2. RESULTS AND DISCUSSION 2.1. Ternary catalytic systems (L2ZrCh+MAO)/TIBA Propylene polymerization. The results on propylene polymerization with ternary systems derived from precatalysts 1 and 2 under the conditions of preactivation with MAO at low molar ratio (AlMAo/Zr=2Q-30Q mol/mol) with further activation with TIBA also at low molar ratios (AlTiBA/Zr=100-1500 mol/mol) are presented in Table 1. Table 1. Propylene polymerization 8 with catalytic systems (1+MAQ)/TIBA and (2+ MAO)/TIBA. Entry

Cat.

solvent

A1 TIBA /Zr b

t,

Y,

(min)

(g)

Ae

l

d

toluene

100

30

0.67

834

2

l

d

heptane

100

32

0.72

845

3

1

heptane

100

20

0.77

1455

4

1

heptane

200

20

1.08

2010

5

1

heptane

300

20

1.32

2371

6

1

heptane

400

20

1.06

1995

7

1

heptane

600

17

0.88

1961

8

2

heptane

600

30

0.23

567

9

2

heptane

800

30

0.62

1510

1

10

2

heptane

1000

10

0.80

5738

11

2

toluene

1000

8

0J6

8700

12

2

heptane

1200

20

0.49

1804

13

2

heptane

1500

30

0.41

997

"Polymerization conditions: the catalysts were preaetivated by dissolving in M A O solution in toluene so that AlMiy}/Zr=3Q0 mol/mol if not specially specified; solvent = 30 mL; [Zr]=l-10" 4 mol/L (Cat. 1), 3-10"s mol/L (Cat. 2); propylene pressure 0.8 atm; 30 °C (Cat. 1), 20 °C (Cat. 2 ) . b Molar ratio in mol/mol; c Activity in (kg PP/(mol Zr h a t m ) ; d A1 MAO /Zr=100 mol/mol.

Both the catalysts show no activity at very low molar ratios A1MAO/Zr~20 mol/mol under the preactivation conditions followed by activation with TIBA in a wide range of AlTiBA/Zr molar ratios. One can see that (i) when preaetivated

N .M. Bravaya et al.

80

with MAO at AIMAO/ZI^OO mol/mol both the catalysts show an incremental increase in activity with an increase in the AITIBA/ZT molar ratio up to an highest values at AlTIBA/Zr=300 (entries3-5, Cat. 1) and 1000 (entries 8-10, Cat.2) followed by a decrease in the activity at higher concentrations of TIBA (entries 6,7 and 12,13, respectively); (ii) the ternary catalytic systems show similar (entries 1,2, Cat. 1) or comparable (entries 10,11, Cat. 2) activities in the medium of toluene and heptane. Comparison of activities of catalysts 1 (2) under their activation with MAO and MAO/TIBA under other optimized conditions is presented in Figure 1 (a, b, respectively). One can see that it is possible to reach much higher or comparable activity of the catalysts in ternary systems at much lower MAO charges. a)

1

AlMAO/Zr= 500 mol/mol 0

b)

15

2

AlMAO/Zr= 300 mol/mol AlTIBA/Zr= 300 mol/mol

A, kgPP/(mmol Zr h atm)

A, kgPP/(mmol Zr h atm)

2

10

AlMAO/Zr= 6000 mol/mol 5

AlMAO/Zr= 500 5C0 mol/mol moVmol AlTIBA/Zr= 500 mol/mol 5OOmol/mol

0

Fig. 1. Comparison of activities of catalysts 1 (a) and 2 (b) in propylene polymerization under their activation with MAO (left columns) and MAO/TIBA (right columns) under other similar conditions.

Catalyst intermediates under preactivation conditions. Combined ! H NMR and UV-vis. studies allowed one to conclude what are catalytic intermediates under conditions of preactivation. 'H NMR analysis of the reaction products of 2 ([Zr]= 4-10"2 mol/1) with MAO showed the formation of monomethylated zirconocene (I) at AlMAo/Zr=40 mol/mol (Zr-Me, 0.87, 0.95 ppm). An increase in the AlMAff/Zr molar ratio to 150 led to the formation of the LaZrMeCl-MAO complex (II) (-1,13 ppm), as well as binuclear cationic complexes (III) ([L2ZrCl(|i-Me)MeZrL2]+[ClMAO]"5 -0.95, -1.66 ppm) and (IV) ([L2ZrMe(uMe)AlMe2]+[ClMAO]", -1.46 ppm). However, NMR experiments were conducted at high concentrations of reagents and can be irrelevant to reaction products formed at lower catalyst concentrations. Fig. 2a shows the UV-vis, absorption spectra of the 1/MAO system measured in toluene at different AlMAo/Zr molar ratios ([Zr]=8-10^* mol/1, and the AlMAo/Zr ratio was varied from 10 to 3000 mol/mol). The matrix consisted of these spectra was subjected to principal component analysis (PCA) [20]. The PCA results evidenced the

13, Modification of Homogeneous Metcdlocene Catalysts

81

formation of only three light-absorbing reaction products in this system: I, II, and either ([L2ZrMe]+[ClMAO] (V) or ([L2ZrMe(u-Me)AlMe2]+[ClMAO] (IV) [21], the latter formed at high AlMAo/Zr molar ratios. The spectra of individual reaction products (Fig. 2a, dash lines) were resolved using parameterized matrix self-modeling method [20]. PCA procedure makes it possible to represent each spectrum as a point in the basis of significant PCA vectors. Fig. 2b shows twodimensional representation of the experimental and theoretical spectra for the 1/MAO system in the basis of two main PCA vectors. The observed trajectory of "spectrum-point" describes the spectral transformations which take place on going from one to another reaction product. The fractional contributions of the reaction products along this trajectory can be estimated assuming equal molar absorption coefficients for all components (Fig 2c). So, only three reaction products are detectable at lower catalyst concentrations: monomethylated zirconocene I (the main product at low AlMAo/Zr molar ratios), cationic species IV or V formed at high A1MAO/& molar ratios, and intermediate polarized complexes of monomethylated zirconocene with MAO II formed under conditions ofpreactivation. For the 2/MAO catalytic system, PCA treatment of the UV-vis. absorption spectra measured at different AlMAo/Zr ratios led to the same conclusions.

0.0 AW

450

500

550

Wavelength / titn

Fig. 2. (a) Area-normalized UV-vis. spectra of the system 1/MAO at varied molar ratios of AIMAQ/ZT. Dash lines show the spectra of individual reaction products as calculated using parameterized matrix self-modeling method: /c - LjZrMeCl, 2c - LjZrMeCl-MAO, 3c ([LaZrMe]+[ClMAO] or ([L2ZrMe(p,-Me)AlMe2]+[ClMAO]; (b) Two-dimensional representation of the experimental and theoretical (indices c) spectra for the 1/MAO system in the basis of two main PCA vectors (p, and p2) ([Zr]=8.0'10"4 M, AWc/Zr mol/mol: 0 (1), 10 (2), 20 (3), 40 (4), 60 (5), 120 (6), 240 (7), 500 (8), 1000 (9), 1650 (10), 3000 (11)). (c) Fractional contributions of the reaction products lc, 2c, and 3c as a function of the AlMAo/Zr molar ratio.

Reaction products of MAO with TIBA (real activators). Reactions of MAO with TIBA were monitored by *H NMR and allowed one to conclude that an increase in the TIBA concentration leads, as illustrated by Fig.3, to the successive: (i) formation of modified MAO (MMAO) due to alkyl groups

82

N ,M. Bravaya et al.

exchange with a simultaneous decrease in the association degree of MAO (spectrum b); (ii) formation of tetraisobutylalumoxane (TIBAO) as the main product at about 30 mol % of TIBA (spectrum c), and (iii) formation of a mixture of TIBAO and polyisobutylalumoxane (IBAO) at equimolar ratios of reagents (spectrum d). In the latter case, the molar ratios of AIMAO/AITIBA are very similar to those providing a high activity of ternary catalytic systems. The results allow one to conclude that IBAO and TIBAO are activators in the examined ternary catalytic systems. Me

MAO

O (0

a

Me

A l —)-O O— A l Al

\

Jnn

Me

A i

M e

'B Bu

—O O

MMAO M MA O

A ll — C O o

Al

i

2.0

1.6

1

O

—AC

B u

c

Al

iB

u

'B u

A"

1.2 1.2

b

u

i

Bu

i 'B u ^ B u

\

B u

Al i'B B

Al

TIBAO TIB AO

2.4

i

O

n

O

R

iB

Al^—O Al O n

A Al ( R R

i

u

+

i

)BB u"

B uu^ B

;BBu^ u

Al

O

Al

i

IBAO IB A O

iB u ^'Bu

d

TIBAO TIB AO A.

0.8

0.4

-0.0

-0.4

-0.8

(ppm (PPm))

Fig. 3. Fragments of *H NMR spectra of MAO (a) and reaction mixtures of MAO + TIBA (b-d) at varying molar ratios of AIXIWAIMAO (mol %): (b) - 6, (c) - 30, (d) -100.

2.2, Promoting effect of Lewis bases on the catalytic properties in propylene polymerization

of

For the 3Me/Ph3CB(C6Fs)4 (TB)/TIBA catalytic system in propylene polymerization it has been shown for the first time that the activity of the system can multiply be increased by introduction of nucleophilic reagents as a co-solution with zirconocene at their stoichiometric amounts. One can see from the Fig.4a that about 30-fold increase in the catalyst activity can be reached in the presence of aniline-type amines (Fig.4a), while trialkylamines, phosphines, and diphenyl ether deactivate the catalyst. The observed "amine effect" can result in an increased efficiency of active sites initiation at complexation with sterically demanded LB or with LB-TIBA complexes due to a decrease in the energy barrier for counterion displacement [19]. It is probable that weakening of ion-counterion interaction is achieved via delocalization of a charge either on the anion or cation as in [22].

13, Modification of Homogeneous Metcdlocene Catalysts

83

Fig. 4. Effect of LBs on the activity in propylene polymerization of (a) 3Me/TB/TIBA and (b) 4Me/X (X=MAO or TB/TIBA) systems (toluene, 30 DC, propylene pressure 6 atm).

The activity of syndiospecific zirconocene 3Me is only slightly increased in the presence of NPh3 under activation with TB/TIBA; however, about twice increase in activity was observed under MAO activation (Fig.4b). The most pronounced effect of NPh3 was observed in propylene polymerization with hafnocene 4Me (Table 2). The catalyst activated with MAO gives rise only to trace amounts of PP (entry 1). Introduction of Ph3N makes the promoting effect on the catalyst productivity under activation with MAO (entry 2). Combined activator TB/TTBA makes the catalyst much more active (entry 3). However, less stereoregular sPP is formed in this case compared to that with MAO-activated system. Catalytic system 4Me/Me2NHPhB(C6Fs)4 (DMAB)/TIBA gives rise to high-molecular-weight sPP of higher stereoregularity but with low activity (entry 4), probably, due to catalyst deactivation in the presence of MeaNPh eliminated in the reaction of cationic active species formation. Similar activity was observed when (Ph2CCpFluHfMe2+Me2NPh) was activated with TB/TIBA (entry 5). Highly active catalyst was obtained under introduction of NPh3 (entries 6-9). Five-fold increase in the Ph3N amount leads to about threefold decrease in the catalyst activity, lowering of Mw and PDI (entry 9). Increase of AlTiBA/Zr molar ratio in amine-free catalytic systems is accompanied by a linear decrease in the activity and lowering of PDI values (entries 10,11 vs. 3). The diversity of active species formed in the absence of amine (e.g., entry 10) and at different ways of amine introduction (as solution with hafnocene (entry 6), TB (entry 7), or that with TIBA (entry 8)) should be mentioned. The catalytic systems show different rates of chain propagation and chain transfer under other similar conditions. One can find the evidences for different effects of coordinating substrates on the properties of operating active species by comparison of GPC curves (Fig.5), activities, and stereoregularities (Table 2) of sPPs obtained in the absence of amine (entry 10) and those in the presence of NPh3 introduced either as complex with hafnocene (entries 6, 9) or as the complex with TIBA (entry 8).

N.M. Bravaya et at.

84

Table 2., Results on propylene polymerizations*1 with 4Me:in combination with different activators, such as MAO, TB/TIBA, and DMAB/TIBA, as well as in the presence ofPh3N. Entry

Activator

t,

Molar ratio Al:Hf:B:N

(min)

Ab

Y,

te)

rr (%)

-

-

-

n.d.

n.d.

87

13.5

1123000

3.50

76

2.S

0.9

1538000

2.18

83

0.5

1.3

n.d.

D-d.

n.d.

1

MAO

1340:1:0:0

30

Traces

2

MAO

1300:1:0:1

63

1.1

0.9

3

TB

90:1:1:0

30

14.3

4

DMAB

90:1:1:0

72

5

C

TB

40:1:1:1

20

6

TB

7

MJMn

-

90:1:1:1

4.5

17.3

105.0

917000

5.40

60

d

100:1:1:1

6.0

11.5

57.0

1580000

2.36

70

B

TB

S

TB

130:1:1:1

8.5

6.7

37.5

2169000

1.69

73

9

TB

100:1:1:5

7.5

7.0

29.0

727000

2.50

75

10

TB

150:1:1:0

60

13.5

7.6

1281000

2.30

65

11

TB

200:1:1:0

30

2.3

3.5

n.d.

n.d.

60

"Polymerization conditions: the catalyst was prepared as toluene solution with PhsN if not specially notified, 100 ml of toluene, 30 °C, propylene pressure 6 atm; b Activity in kg PP/(mol Hf min atm);G The catalyst was introduced as co-solution with MeaNPh;d The order of reagents loading was: toluene+TTBA+toluene solution of 4Me+(toluene solution of TB with PhaN); e The order of reagents loading was: toluene+(toluene solution of TIBA with PhjNJ+toluene solution of 4Me+toluene solution of TB.

Thus both productivities and stereoselectivities of the catalyst in entries 8,9 are of about similar values, Mw of generated sPP being about 3 times higher when amine was introduced as the NPhj-TIBA complex. In an excess of TIBA in the absence of amine (entry 10), sPP with much lower activity and stereoregularity is formed compared to that with the NPhs-TIBA system (entry 10 vs. 8), Mw of sPP formed in this case being about twice lower than that in entry 8 is about twice higher than that in entry 9, Increase of Al-nBA/Hf molar ratio in the absence of amine is accompanied by a decrease in the activity. The most surprising effect was a sharp decrease in stereoregularity at sPP in the increased A1TIHA/Hf molar ratios. Stereoblock syndio/atactic PP is formed in excess of TIBA (entries 10, 11). Reversible coordination of TIBA multiply perturbing the geometry of the catalyst during chain growth [2] was proposed as a working hypothesis to explain the effect. One can see that the (4Me+NPh3)/TB/TIBA system shows very high activity and produce low stereoregular sPP with high PDI at AlT1BA/Hf=9G mol/mol and N/Hf=l mol/mol (entry 6).

13, Modification of Homogeneous Metallocene Catalysts

85

At the same time, multiple Gauss fitting of the curve shows the presence of all the peaks observed for sPPs of entries 8-10 with additional low-molecular peak, probably, arising due to a high value of heat evolution at the initial stage of the polymerization process. 1.4

8

1.2

9 10

d w t/d(lo g (MW))

1.0

0.8

6 0.6

0.4

0.2

0.0 7.0

6.5

6.0

5.5

5.0

4.5

4.0

log(MW)

Fig. S, GPC curves of sPPs obtained with the PhzCCpFluHfMe3/TB/TIBA system in the absence and presence of PhjN (curve numbers correspond to those in Table 2),

3. CONCLUSIONS Thus, the above-discussed experimental data show that both TIBA and Ph3N can be used for modification of metallocene-derived catalytic systems with MAO and TB activators. It should be mentioned that almost all present-day approaches to controlling the activity and stereoselectivity of metallocene catalytic systems are primarily based on the use of either new metallocene complexes or new activators. Considering the results of this study, we would like to attract the attention to poorly investigated possibilities of controlling the activity and stereoselectivity of metallocene systems that are offered by the addition of TIBA or LBs. Referencei [1] A. N. Panin, Z. M. Dzhabieva, P. M. Nedorezova, V. I. Tsvetkova, S. L. Saratovskikh, O. N. Babkina, N. M. Bravaya, J. Polym. Sci. A: Polym. Chem. 39 (2001) 1915-1930. [2] O. N. Babkina, N. M. Bravaya, P.M. Nedorezova, S. L. Saratovskikh, V. I. Tsvetkova, Kinet. Catal. 43 (2002) 341-350.

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[3] Y. X. Chen, M. D. Rausch, J. C. W. Chien, J. Polym. Sci. A: Polym. Chem. 33 (1995) 2093-2108. [4] F. Q. Song, M. D. Hannant, R. D. Cannon, M. Bochmann, Maeromol. Symp. 213(2004)173-185. [5] C. Gotz, A. Rau, G. Luft, Maeromol. Symp. 178 (2002) 93-107. [6] W. Michiels, A. Munozescalona, Maeromol. Symp. 97 (1995) 171-183. [7] R. Kleinsehmidt, Y. Leek, M, Reffke, G. Fink, J. Mol. Catal. A: Chem. 148 (1999)29-41. [8] M. L. Britto, G. B. Galland, J. Henrique, Z. Dos Santos, M. C. Forte, Polym. 42 (2001) 6355-6361. [9] W. Wang, Z. Q. Fan, Y. B. Zhu, Y. H. Zhang, L. X, Feng, Europ. Polym. J. 38(2002)1551-1558. [10] M. Lahelin, E. Kokko, P. Lehmus, P. Pitkanen, B. Lofgren, J. Seppala, Maeromol. Chem. Phys. 204 (2003) 1323-1337. [11] O. M. Khukanova, O. N. Babkina, L. A. Rishina, P. M. Nedorezova, N. M. Bravaya, Polymery 45 (2000) 328-332. [12] P. M. Nedorezova, V. I. Tsvetkova, A. M. Aladyshev, D. V. Savinov, T. L. Dubnikova, V. A. Optov, D. A. Lemenovskii, Polymery 45 (2000) 333-338. [13] M. A. Esteruelas, A. M. Lopez, L. Mendez, M. Olivan, E. Onate, Orrganometallics, 22 (2003) 395-406. [14] K. Musikabhumma, T. Uozumi, T. Sano, K. Soga, Maeromol. Rapid. Common. 21 (2000) 675-679. [15] J. C. Flores, J. C. W. Chien, M. D. Rauseh, Organometallies 13 (1994) 4140-4142. [16] O. Kuhl, T. Koch, F. B. Somoza, P. C. Junk, E. Hey-Hawkins, D. Plat, M. S. Eisen, J. Organomet, Chem. 604 (2000) 116-125, [17] P. Mehrkhodavandi, R. P. Schrock, L. L. Pryor, Organometallies 22 (2003) 4569-4583. [18] P. G. Belelli, M. L. Ferreira, D. E. Damiani, Maeromol. Chem. Phys. 201 (2000) 1458-1465. [19] F. Schaper, A. Geyer, H. H. Brintzinger, Organometallies 21 (2002) 473483. [20] A. G. Ryabenko, E. E. Faingol'd, E. N. Ushakov, N. M. Bravaya, Russ. Chem. Bull, (in press). [21] J.-N. Pideutour, K. Radhakrishnan, H. Cramail, A. Deffieux, . Mol. Catal. A: Chem. 185 (2002) 119-125. [22] J. Zhou, S. J. Lancaster, D. A. Walker, S. Beck, M. Thorton-Pett, M. Bochmann, J. Am. Chem. Soe. 123 (2001) 223-237.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

87

14 Iron(II) Complexes Ligated with 2-Imino-l?10Phenanthroline for Ethylene Activation Wen-Hua Sun*, Suyun Jie, Shu Zhang and Wen Zhang Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China

Abstract A series of iron complexes containing 2-imino-l,10-phenanthrolinyl ligands, LFeCl2 (L=2-(ArN=CR)-l,10-phen), have been synthesized and sufficiently characterized by elemental and spectroscopic analysis as well as by X-ray diffraction analysis. Upon activation with methylaluminoxane (MAO), these iron(H) complexes showed high catalytic activities [up to 4.91 xlO7 g mol'fFe) h"1] for ethylene oligomerization. The distribution of oligomers produced follows Schluz-Flory rule with high selectivity of a-olefins. Both the steric and electronic effects of coordinative ligands affect the catalytic activity and the properties of the resultant products. The parameters of the reaction conditions were also investigated to explore the catalytic potentials of these complexes. 1. INTRODUCTION a-Olefins are major industrial reactants that are extensively used in the preparation of detergents, lubricants, plasticizers, oil field chemicals as well as monomers for copolymerization. The ethylene oligomerization is currently one of the major industrial processes for the production of a-olefins. In the past decade significant progress was achieved in the development of late-transition metal catalysts for ethylene oligomerization. In 1998, extremely active iron- and cobalt-based catalysts bearing 2,6-bis(imino)pyridyl ligands for the ethylene polymerization (to afford linear polyethylene) had been discovered independently by Brookhart [1], Gibson [2]. By tuning the steric and electronic properties of the ligands, the catalytic products of these metal complexes varied

88

W-K Sun et at.

from polyethylene to oligomers (A, Chart 1) [3], in which both the catalytic activity and selectivity for a-olefins are highly promising.

Chart 1. Complex models of iron(II)-based catalysts

We have been exploring to find the suitable tridentate metal complexes, the late-transition metal complexes containing 259-bis(imino)-l»10-phenanthrolinyl ligand for the ethylene polymerization/oligomerization. However, we found that the iron complexes (B, Chart 1) only showed low activities for ethylene polymerization [4]; this result was also confirmed by Gibson group [5]. It was thus assumed that the nitrogen atom of the additional imino group can coordinate to the active iron center which is a necessary for the coordination of ethylene for oligomerization/polymerization [6]. Therefore, the additional imino group in B should be thus eliminated to verify this hypothesis. Since the synthesis of 2-formyl-, 2-acetyl- and 2-benzoyl-l,10-phenanthrolines would be thus required to achieve the above purpose, various 2~imino-l,10phenanthrolinyl ligands and the corresponding iron(ll) complexes containing these ligands have thus been synthesized. Since these iron(ll) complexes showed both high activity and notable selectivity for ethylene oligomerization to afford linear a-olefins, we herein report our explored results for ethylene oligomerization by the and corresponding iron(ll) complexes containing 2imino-l,10-phenanthrolinyl ligands under various reaction conditions. 2. EXPERIMENTAL Synthesis of the ligands. A reaction mixture of 2-acetyl-, 2-formyl- or 2benzoyl-l,10-phenanthroline and 2,6-disubstituted aniline was reacted in absolute ethanol, toluene or tetraethyl silicate using /s-toluenesulfonic acid as catalyst. After the solvent was removed, the residue was eluted with petroleum ether/ethyl acetate on an alumina column. The second eluting part was collected and concentrated to give the desired ligand in acceptable yield. Synthesis of the iron(II) complexes. The ligand and one equivalent of FeCl2-4H2O were added together in a Schlenk tube that was purged three times with argon and then charged with THF. The reaction mixture was stirred at room temperature for 9 h. The resulting precipitate was filtered, washed with

14. Fe(H) Ligatedwith 2~Imina~ 1,1Q-Phenanthraline for Ethylene Activation

89

diethyl ether and dried in vacuum. All the iron (IT) complexes were prepared in high yields in this manner. 3. RESULTS AND DISCUSSION 3,1. Synthesis and Characterization The 2-imino-l,10-phenanthrolinyl ligands [1-12, 2-(ArN=CR)-l,10-phen] were prepared by condensation reaction of aldehyde or ketones with corresponding substituted anilines using j?-toluene sulfonic acid as catalyst (Scheme 1). Because of the difference in the reactivities between the aldehydes (the ketones) and alkyl- and halogen-substituted anilines, the various solvents such as ethanol, toluene or tetraethyl silicate were employed in order to improve the product yields. The 2-imino-l,10-phenanthrolinyl ligands can be classified according to the nature of R on the imino-C as methyl-ketimine (R=Me, 1- 6), aldimine (R=H, 7-9) and phenyl-ketimine (R=Ph, 10-12), and all compounds were sufficiently characterized and confirmed by 1R, 'H and I3C NMR spectra as well as by elemental analysis.

THF, r.t 1-12

Ka) R

2(a) 3(a)

1a- 12a

«M

S{a) 6{a) 7(a) 8{a) 9(a) 10{a) 11 (a) 12(a)

Me Me Me Me Me Me

R1 Me Et

i-Pr

F

Cl

Br

H

H

Me Et

H

Ph

i-Pr

Me

Ph

Ph

Et

i-Pr

Scheme 1. Synthesis of the ligands 1 - 1 2 and the IronfTI) complexes l a - 12a,

The iron(TI) complexes la-12a were easily prepared by treating the corresponding ligand with one equivalent of FeCl2-4HzO in THF at room temperature under argon (Scheme 1). The resulting complexes were precipitated from the reaction solution and separated as blue (purple or brown) air-stable powders. All the complexes were characterized by FT-IR spectra and elemental analysis. In the IR spectra, the stretching vibration bands of C=N of these iron(II) complexes (1602-1614 cm"1) apparently shifted to lower wave number and the peak intensity greatly reduced, as compared to the corresponding ligands (1618-1656 cm"1), indicating the coordination interaction between the

W.-H. Sun et al.

90

imino nitrogen atom and the metal cation. Their structures were deteremined by the single-crystal X-ray diffraction analysis. Single crystals of complexes 2a suitable for X-ray diffraction analysis were obtained by slow diffusion of diethyl ether into its methanol solution under argon atmosphere, while crystals of 9a were grown through slowly layering of the chloroform solution of ligand 9 over the ethanol solution of FeCl2 in a Schlenk tube under argon atmosphere. According to their structures, the coordination geometry around the iron center can be described as a distorted trigonal bipyramidal, in which the nitrogen (next to the imino-C) of the phenanthrolinyl group and two chlorides compose an equatorial plane. Their crystal structures are shown in Figure 1.

Figure 1. Crystal structures of 2a and 9a. Hydrogen atoms have been omitted for clarity.

3.2. Ethylene Oligomerization The prepared iron(IT) complexes exhibited high catalytic activities for ethylene oligomerization in the presence of MAO to afford a-olefins with high selectivity (ethylene 10 atm). The detailed results are summarized in Table 1. The distribution of oligomers follows Schulz-Flory rules in all cases, which is characteristic to the constant a; where a represents the probability of chain propagation [a = rate of propagation/ {(rate of propagation) + (rate of chain transfer)} = (moles of Cn+2)/(moles of Cn)] [7]. The a values are determined by the molar ratio of Ci2 and C14 fractions. 3,2.1. Effects of the molar ratio ofAl/Fe and reaction temperature. Ethylene oligomerization with 2a - MAO catalyst was investigated under various reaction conditions (the Al/Fe molar ratio, temperature etc.). The catalytic activities (calculated based on the yield of both oligomers and lowmolecular-weight waxes) initially increased and then decreased upon increasing the Al/Fe molar ratio (200 to 2000), whereas no significant changes were observed in the a value. In contrast, both the activity and a value initially increased, and then decreased upon increasing the temperature; however, no significant increases were observed in the activity. Complex 2a exhibited the

14. FeflJ) Ligatedwith 2-Immo-l,10-Phenanthroline for Ethylene Activation highest activity of 4.91 xlO7 g mol^CFe) h"1 at the Al/Fe molar ratio of 1000:1 and 40 °C under 10 atm of ethylene pressure. Table 1. The results of ethylene oligomerization by complexes la-12a/MAO a

oligomers entry

cat.

Al/Fe

waxes

7*(°C) -

A:

a

% a-O"

Aj

1

2a

200

40

0.12

0.68

>99

1.01

2

2a

500

40

2.12

0.64

>9S

1.56

3

2a

1000

40

4.91

0.62

>94

14.6

4

2a

1500

40

2.55

0.62

>97

9.13

5

2a

2000

40

0.75

0.64

>98

1.25

6

2a

1000

20

1.64

0.49

>96

10.1

7

2a

1000

30

2.14

0.55

>95

26,3

g

2a

1000

50

3.55

0.61

>93

5.87

9

2a

1000

60

1.44

0.44

>95

4.88

10

la

1000

40

3.89

0.67

>96

102

11

3a

1000

40

0.94

0.50

>9S

0.21

12

4a

1000

40

2.37

0.37

>79

trace

13

Sa

1000

40

3.51

0.52

>79

trace

14

6a

1000

40

4.06

0.61

>80

65.5

15

7a

1000

40

1.33

0.58

>94

48.6

16

8a

1000

40

0.16

0.54

>99

trace

17

9a

1000

40

0.90

0.48

>97

0.88

18

10a

1000

40

1.27

0.57

>91

304

19

lla

1000

40

2.30

0.52

>95

3.25

20

12a

1000

40

0.13

0.50

>98

3.18

E

General conditions: 2 junol cat.; reaction time: 1 h; solvent: 100 mL toluene; ethylene pressure: 10 atm. * Reaction temperature. c Activity for oligomers: 107 g mor'(Fe) h"1. 4 Activity for lowmolecular-weight waxes: 10s g mof^Fe) h"1. B% a-olefm content determined by GC and GC-MS.

3.2.2. Effect of the iigand environment. Note that the variation of the R substituent on the imino-C of ligands, 2(ArN=CR)-l,10-phen, resulted in tuning the catalytic performance. Aldimine (R=H) and phenyl-ketimine (R=Ph) complexes showed relatively lower catalytic activities than the corresponding methyl-ketimme (R=Me) complexes.

91

92

W.-H. Sun et al.

Furthermore, the R substituent had different influences on the catalytic performances of methyl- or phenyl-ketimine and aldimine analogues. For the 2,6-dialkyl-substituted ketimine and aldimine complexes, both the methylketimine complex 2a and the phenyl-ketimine complex l l a containing 2,6diethyl groups on the phenyl ring of the imino nitrogen, showed the highest activity among their analogues. However, the aldimine complex 8a showed much lower activity under the same reaction conditions (entry 3, 19 and 16 in Table 1). Comparing the complexes containing ketimine or aldimine ligand which possesses 2,6-diisopropylphenyl group on the imino nitrogen, both 3a and 9a (entries 11 and 17 in Table 1) showed much higher catalytic activity than 12a (entry 20 in Table 1), which also showed lower activity than its analogues (entries 18 and 19 in Table 2), perhaps due to the bulky phenylketimine ligand. In general, all methyl-ketimine complexes bearing electrondonating alkyl groups showed high catalytic activity and good selectivity for aolefins. On the contrary, relatively lower selectivity was observed with the complexes containing electron-withdrawing halogen groups, such as complexes 4a - 6a, although these complexes showed high activities. The substituents on the imino-N aryl ring were found to show great influence toward the catalyst performances of both the ketimine and aldimine complexes. For instance, the 2,6-dialkyl-substituted methyl-ketimine complexes la-3a, decrease in the catalytic activity was observed upon increasing the steric bulk on R1, and this could be demonstrated by comparing the 2,6-diisopropylsubstituted 3a with the 2,6-dimethyl-substituted la or 2,6-diethyl-substituted 2a (entry 11 vs. entry 10 or 3 in Table 1). The steric bulk of the isopropyl groups at the o?ffe-positions of imino-N aryl ring of complex 3a may prevent the access (coordination) of ethylene to the active center in the catalytic system, therefore leading the decrease in the catalytic activity. Furthermore, the bulkier the substituents, the smaller a value and a smaller amount of low-molecular-weight waxes were produced. Complexes 4a-6a, containing halogen groups, exhibited comparable catalytic activity and relatively lower selectivity of a-olefins in the oligomerization of ethylene than complexes bearing only alkyl groups. In the catalytic systems of 2,6-dihalogen-substituted complexes 4a-6a, the bulkier substituents at the or^o-positions of imino-N aryl ring resulted in higher catalytic activities as well as higher a value (bromo- > chloro- > fluoro-, entries 12-14 in Table 1). For the aldimine complexes 7a~9a, 2,6-dimethyl-substituted complex 7a displayed the higher catalytic activity of 1.33xlO7 g mol'l(Fe) h"1 (entry 15 in Table 1), while a much lower catalytic activity was obtained for 2,6-diethylsubstituted complex 8a (entry 16 in Table 1) under the same reaction conditions. For the phenyl-ketimine complexes, complex 12a bearing bulkier isopropyl groups at the ortte-positions of the aryl ring had much lower oligomerization

14. Fe(II) Ligatedwith 2-lmmo-l,10-Phenanthroline for Ethylene Activation

93

activity than the 2,6-dimethyl-substituted 10a and the 2,6-diethyl-substituted l l a , probably because of the cooperative interaction of bulkier isopropyl groups on the imino-N aryl ring and bulkier phenyl on the imino-C. 3.2.3, Characterization for low-molecular-weight waxes. In many cases, some low-molecular-weight waxes were obtained as higher oligomers in addition to lower oligomers. Characterized by IR spectra recorded using KBr disc in the range of 4000-400 cm"1, the waxes can be confirmed to be mainly linear a-olefins from the characteristic vibration absorption bands of C=C and various C-H bonds. ! H and 13C NMR spectra of the waxes obtained by complex la/MAO were recorded in o-dichlorobenzene-rf4 using TMS as the internal standard. The NMR spectra of the waxes were shown in Figure 2 and the assignments were determined according to the literatures [8,9]. The 13C NMR spectra further demonstrated that linear a-olefins of the waxes absolutely predominantly existed in the waxes and the single peaks at S 139.14 and 114.17 ppm showed the property of vinyl-unsaturated chain end. The obtained average molecular weight from lH NMR indicated that the carbon number of the waxes was about 40. -CH,-

-CH-

(a) (b)

JL

VJ

Figure 2. NMR spectra of the waxes obtained by complex la/MAO. (a) I3C NMR; (b) JH NMR.

4. CONCLUSIONS A series of tridentate iron(II) complexes bearing 2-imino-l,10phenanthrolinyl ligands have been synthesized and fully characterized. Upon treatment with MAO, these iron(ll) complexes showed high catalytic activities of up to 4.91 xlO7 g moF'CFe) h"1 for ethylene oligomerization with high selectivity for a-olefins. Both the R on the imino-C and the substituents on the N-aryl rings strongly affect the catalytic activity, distribution of oligomers, and selectivity for a-olefins due to their different steric and electronic properties.

94

W.-H.Sunetal

The methyl ketimine complexes were proved to be relatively more active catalysts than either the corresponding aldimine or phenyl ketimine complexes under the same reaction conditions. Electron-donating groups placed on the Naryl rings increased the selectivity for ct-olefins. The placement of bulkier oalkyl groups on the N-aryl rings led to the reduced activity because of steric interaction, however, bulkier halogen groups gave the reverse effect. Acknowledgements The project was supported by NSFC 20473099 along with National 863 Project (2002AA333060), and partly sponsored by CNPC Innovation Fund (04E7054). References [1] B. L. Small, M. Brookhart, and A. M. A. Bennett, J. Am. Chem. Soc. 120 (1998) 4049-4050. [2] G. J. P. Britovsek, ¥ . C. Gibson, B. S. Kimberley, P. J. Maddox, S. J. MeTavish, G. A. Solan, A. J. P. White, and D. J. Williams, Chem. Commun. (1998)849-850. [3] B. L. Small, and M. Brookhart, J. Am. Chem. Soc. 120 (1998) 7143-7144. [4] L. Wang, W. -H. Sun, L. Han, H. Yang, Y. Hu, and X. Jin, J. Organomet. Chem. 658 (2002) 62-70. [5] G. J. P. Britovsek, S. P. D. Baugh, O. Hoarau, V. C. Gibson, D, F. Wass, A. J. P. White, and D. J. Williams, Inorg. Chim. Acta 345 (2003) 279-291. [6] S. Ameerunisha, J. Schneider, T. Meyer, P. S. Zacharias, E. Bill, and G. Henkel, Chem. Commun. (2000) 2155-2156. [7] (a) G. V. Z. Schulz, Phys. Chem., Abt. B 30 (1935) 379-398. (b) G. V. Z. Schulz, Phys. Chem., Abt. B 43 (1939) 25-46. (c) P. J. Flory, J. Am. Chem. Soc. 62 (1940) 1561-1565. (d) G. Henrici-Olive, and S. Olive, Adv. Polym. Sci. 15 (1974) 1-30. [8] G. B. Galland, R. F. De Souza, R. S. Mauler, and F. F, Nunes, Macromolecules 32 (1999) 1620-1625. [9] G. B. Galland, R. Quijada, R. Rojas, G. C. Bazan, and Z. J. A. Komon, Macromolecules 35 (2002) 339-345.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

95

15 Polymerization of 1-Hexene and Copolymerization of Ethylene with 1-Hexene Catalyzed by Cationic Half-Sandwich Scandium Alkyls Yunjie Luof and Zhaomin Hou* Organometallic Chemistry Laboratory, RIKEN (The Institute of Physical and Chemical Research), Hirosawa 2-1, Wako, Saitama 351-0198 Japan, and PRESTO, Japan Science and Technology Agency (JSI), Japan

Abstract The combination of half-sandwich scandium bis(alkyl) complexes, such as (CsMe4SiMe3)Sc(CH2SiMe3)2(THF) (1), with 1 equiv of [Ph3C][B(C6Fs)4] showed high activity for the polymerization of 1-hexene. Such complexes could also promote the copolymerization of ethylene and 1-hexene with high activity to produce ethylene/1 -hexene copolymers containing isolated butyl branches in the chain backbone. The copolymerization activity of the present catalyst is much higher than that of the homopolymerization of either monomer, thus constituting a rare example of a homogeneous catalyst system that shows significant positive "comonomer effect" in the copolymerization of two different monomers. 1. INTRODUCTION The development of efficient homogeneous catalysts for the polymerization and copolymerization of ethylene and a-olefins to synthesize high performance polymer materials has been the subject of intense scrutiny in both academic and industrial researches [1]. Over the past two decades, organo rare earth metal complexes have received much attention for application as homogeneous polymerization catalysts [2,3]- Generally, neutral organo rare earth metal complexes can show high activity for the polymerization of ethylene and polar monomers without requirement of a eoeatalyst. However, most of these

96

Y. Luo and Z, Hou

complexes usually show no or very low activity for the polymerization of higher olefins such as cc-olefins, conjugated dienes, cyclic oleflns, and styrene [4,5], In particular, the copolymerization of ethylene with an a-olefm by a rare earth metal catalyst remained scarce [4a,k,n]. Recently, more attention has been directed to cationic rare earth metal alkyl complexes because of their high potential as catalysts for olefin polymerization [3,6,7]. Recent work in our group has demonstrated that cationic half-sandwich rare earth metal alkyls, such as [(CsMe4SiMe3)Sc(CH2SiMe3)]+ and [Me2Si(C5Me4)C"-PCy)YCaCH2SiMe3)Y(/^PCy)(C5Me4)SiMe2]+, which are generated by treatment of the corresponding neutral dialkyl precursors with 1 equiv of [Ph3C][B(C6Fs)4], can serve as unique catalysts for polymerization and copolymerization of various olefins, such as syndiospecific copolymerization of styrene with ethylene [6a], alternating copolymerization of ethylene with norbomene (or dicyclopentadiene) [6b,e], terpolymerization of ethylene, dicyclopentadiene, and styrene [6c], and isospecific 3,4-polymerization of isoprene [6d]. We wish to report here that such cationic half-sandwich scandium alkyl species can also act as a highly active catalyst for the polymerization of 1-hexene and the copolymerization of ethylene with 1-hexene [8]. In particular, the activity for the copolymerization of ethylene with 1-hexene is the highest ever reported for a rare earth metal catalyst, and could be compared with those reported for the most active group 4 metal-based catalyst systems [9]. 2. EXPERIMENTAL General Considerations. All the manipulations were performed under pure argon with rigorous exclusion of air and moisture using standard Sehlenk techniques and an Mbraun glovebox. Ethylene (Takaehiho Chemical Industrial Co., Ltd.) was purified by passing through a Dryclean column (4 A molecular sieves, Nikka Seiko Co.) and a Gasclean CC-XR column (Nikka Seiko Co.). [Ph3C][B(C,jF5)4] was purchased from Tosoh Finechem Corporation and used without purification. 1-Hexene (Kanto Chemical Co., Ltd.) was dried by stirring with CaH2 for 24 hours, and distilled under reduced pressure prior to polymerization experiments. Cp'Se(CH2SiMe3)2(THF) (1-7) were prepared according to literature [6a,b,10,l 1]. 'H, 13C NMR spectra of polymer samples were recorded on a JEOL INM-EX 270 spectrometer (FT, 300 MHz for ! H; 75.5 MHz for 13C). The spectra of ethylene-1-hexene copolymers were measured in lsl,2,2-tetrachloroethane-rf2 at 120 °C, while the spectra of poly(l-hexene)s were recorded in CDC13 at 25 °C. Molecular weights and molecular weight distributions of poly(l-hexene)s were determined against polystyrene standard by gel permeation chromatography (GPC) on a HLC-8220 GPC apparatus (Tosoh Corporation). THF was used as

15. Homo- and Capofymerization of 1-Hexene with Ethylene

97

an eluent at a flow rate of 0.35 mL/min at 40 °C. Molecular weights and molecular weight distributions of ethylene/1-hexene copolymers were determined against polystyrene standard by high temperature gel permeation ehromatography (HT-GPC) on a HLC-8121 GPC/HT apparatus (Tosoh Corporation). 1,2-Dichlorobenzene was used as an eluent at a flow rate of 1.0 mL/min at 145 °C. 1-Hexene Hamopolymerization. A typical polymerization reaction is given below (Table 1, run 1). In a 100 mL round-bottom glass flask with a stirring bar, 10 mg (21 /anol) of (CsMe4SiMe3)Sc(CH2SiMe3)2(THF) in toluene (5 mL), and 19 mg (21 /flnol) of [Ph3C][B(C6F5)4] in toluene (8 mL) were introduced sequentially at room temperature. A few minutes later, 1.736 g (21 mmol) of 1hexene was added under vigorous stirring. The polymerization reaction was carried out at room temperature for 15 minutes, Methanol (60 mL) was poured into the flask to precipitate the polymer, which was then separated and dried under vacuum at 60 °C to a constant weight (1.68 g, 97%). Ethylene and 1-Hexene Copolymerization. A typical eopolymerization reaction is given below (Table 2, run 3). In a glove box, 15 mL of toluene, 1.736 g (21 mmol) of 1-hexene were mixed together in a 100 mL two-necked round-bottom glass flask with a stirring bar. The flask was taken outside and attached to a Schlenk line, a well-purged ethylene line, and a mercury-sealed stopper. The flask was placed in a water bath at 25 °C, and ethylene was then introduced under rapid stirring, A reaction mixture of 21 /flnol (10 mg) of (C5Me4SiMe3)Sc(CH2SiMe3)2(THF) and 21 /anol (19 mg) of [Ph3C][B(C6F5)4] in 15 mL of toluene was quickly added into the flask via a syringe under an ethylene counter flow. The polymerization reaction was carried out for 5 minutes, and was then terminated by addition of 2 mL of methanol. The resulting mixture was poured into methanol (400 mL) to precipitate the polymer. The white polymer product was collected by filtration, dried under vacuum at 60 °C to a constant weight (2.26 g). 3. RESULTS AND DISCUSSION J. 1. Polymerization of 1-Hexene The neutral half-sandwich scandium bis(alkyl) complexes Cp'Sc(CH2SiMe3)2(THF) (Cp' = C5Me4SiMe3 (1), CsMes (2), l,3-(SiMe3)2C5H3 (3)) were inert for 1-hexene polymerization. However, on treatment with 1 equiv of [Ph3C][B(CgF5)4] in toluene, these complexes showed high activity for the polymerization of 1 -hexene, with an activity order of 1 > 2 > 3 (Table 1, runs 1, 6 and 7). The average number molecular weight (Mn) of the polymers

Y, Luo and Z, Hou

98

Table 1 Polymerization of 1-Hexene Catalyzed by Cp'Sc(CH2SiMe3)2(THF)/[Ph3C][B(C6F5)4]E

Cp'Sc(CH2SiMe3)2(THF) + [Ph3C][B{C8F6)4] »

toluene

(pp' = C5iyie4SiMe3 (1), C s Me s (2), 1,3-(SiMe3)2CsH3 (3)] run

oat.

[M]/[Sc]

Tv

t

cam.

activity

Mnb

(°C)

(min)

(%)

kg/(mol-Sc-h)

(xlO"3)

MJMnh

1

1

1000

25

15

97

322

5.8

1.65

2

1

1500

25

30

90

446

5.7

1.67

3

1

1000

0

30

85

140

27,7

1.58

4

1

1000

-15

60

87

71

144.1

1.43

5

1

1000

-40

150

78

26

332.5

1.48

6

2

1000

25

15

64

213

5.6

1.58

7

3

1000

25

15

26

86

4.8

1.51

* Polymerization conditions; in toluene; Sc, 21 /anol; [Sc]/[B] = 1/1 (molar ratio); solvent/monomer = 5:1 (v/v). h Determined by GPC against polystyrene standard.

obtained at room temperature was rather low (Mn = 4800-5800), and was independent of the amount of monomer consumed (Table 1, runs 1, 2, 6 and 7). However, when the polymerization was carried out at low temperatures (Table 1, runs 3-5), the molecular weight of the resulting polymers increased dramatically, and reached as high as 332.5 x 103 at -40 °C. These results suggest that a chain transfer reaction must occur rapidly at room temperature but could be suppressed efficiently at lower temperatures. The ! H NMR analysis of an oligomer product (Mn = 3000, MJMn = 1.34) obtained at room temperature revealed the presence of two types of olefinic end groups. One is terminal vinylidene at S4.61 (br s) and 4.73 (br s), which could be formed by fihydrogen elimination after 1,2-insertion, and the other is a internal vinylene unit (£5.37, multiplets), which must result from ^-hydrogen elimination after 2,1insertion [12]. These results indicate that the present polymerization reactions should proceed in both 1,2- and 2,1-insertion fashions, with /J-hydrogen elimination as a chain termination reaction. The GPC curves of the resulting polymers were all unimodal with relatively narrow molecular weight distributions {MJMn - 1.43-1.67), indicative of single-catalyst behavior. Under the same conditions, the analogous complexes of larger metal ions such as (CsMe4SiMe3)Ln(CH2SiMe3)2(THF) (Ln = Y (4), Gd (5), Dy (6), Lu (7)) did not show activity for 1-hexene polymerization, suggesting that the activity of this type of complex is metal dependent. Similar metal dependence was

15. Homo- and Copolymerization of 1-Hexene with Ethylene

99

observed previously in sryrene polymerization and ethylene-norbomene copolymerization [6a-c], Table 2 Ethylene (E) and 1-Hexene (H) Copolymerization Catalyzed by

1 o r 2 + [Ph3e][B(C8F5)4]

toluene, 25 °C

cat.

H

E

t

yield

(mmol)

(atm)

(min)

(g)

activity*

Hcont. c

Mnd

(mol%)

MJMnd

^

1 2

1 1

0 21

1 0

5 15

1.13 1.33

658 258

0 100

21.35 0.49

1.75 1.49

3

1

21

1

5

2.26

1291

13

2.37

2.89

4

1

42

1

5

3.38

1932

23

1.37

2.74

5

1

S4

1

5

3.98

2274

32

1.09

2.16

6

2

21

1

5

0.99

565

2

20.62

2.59

b

Conditions: toluene, 30 mL; Se, 21 /anol; [Sc]/[B] = 1/1 (mol/mol). Given in kg/(molSc-h-atm).c Determined by ! H NMR. Determined by GPC against polystyrene standard,

3,2. Copolymerization of Ethylene with 1-Hexene The combination of (C5Me4SiMe3)Sc(CH2SiMe3)2(THF) (1) with [Ph3C][B(C6Fs)4] also showed high activity for the copolymerization of 1hexene and ethylene at room temperature, yielding the corresponding ethylene1-hexene copolymer, or the so-called linear low density polyethylene (LLDPE) (Table 2). The 1 -hexene content in the copolymer products could be controlled by changing the 1-hexene monomer feed under 1 atm of ethylene. As 1-hexene feed was raised, the incorporation of 1-hexene increased significantly (Table 2, runs 3-5), It is also noteworthy that the polymerization activity of the present catalyst was also increased significantly with the increase of 1-hexene feed, which thus constitutes a rare example of a homogeneous polymerization catalyst system that shows significant positive "comonomer effect" in the copolymerization of ethylene with an o-olefm [13,14]. The activity of the present caMyst system for the copolymerization of ethylene with 1-hexene could reach as high as ca, 2.3 x 103 kg/(mol-Sc-atm-h) at room temperature (Table 2, run 5), which ranks the highest ever reported for a rare earth metal

Y. Luo and Z. Hou

100

catalyst for ethylene/1-hexene copolymerization [4], and could be compared with those reported for the most active group 4 metal catalysts [9]. In the case of 2, the incorporation of 1-hexene was very low (2 mol%) (Table 2, run 6), while with 3-7, no incorporation of 1-hexene was observed under the same conditions. These results are in consistence with the activity of these complexes for 1-hexene homopolymerization. 13C NMR analyses revealed that the resulting ethylene- 1-hexene copolymers contain isolated butyl branches in the polymer chain backbone (Figure 1). No hexene-hexene sequence was formed as evidenced by the absence of <mmethylene carbon peaks ($40—41 ppm) [15], γδ+

δδ+

δδ+

αδ+

βδ+

αδ+

γδ+

βδ+ 4B4

δδ+

3B4 2B4 1B4 + αδ oc8+ 4B 4 B 44

methine methine

γδ y8++ 3B 3 B 44

+ βδ P8 +

1B4

2B44

v»v»*^*^m-A-wv

42

40

38

Figure 1

36

34

32

30

-rp-r

28 28 δ (ppm) 8 (ppm)

26

24

22

20

18 18

16

T 14 14

T3

C NMR spectrum of an ethylene-1 -hexene copolymer (Table 2, run 5).

CONCLUSION We have demonstrated that the combination of a half-sandwich scandium bis(alkyl) complex such as (CsMe4SiMe3)Sc(CH2SiMe3)2(THF) (1) with 1 equiv of [Ph3C][B(C6Fs)4] can act as a highly active catalyst not only for the homopolymerization of 1-hexene but also for the copolymerization of ethylene with 1-hexene. The copolymerization activity of the present catalyst is much higher than that of the homopolymerization of either monomer, thus constituting a rare example of a homogeneous catalyst system that shows significant positive "eomonomer effect" in the copolymerization of two different monomers. This is the first example of efficient ethylene/a-olefin copolymerization catalyzed by a rare earth metal catalyst. The difference in catalytic activity observed among complexes 1-7 suggest that the activity of this type of complex could be tuned by changing the cyclopentadienyl ancillary ligands or the central metal ions in rare earth metal series. Acknowledgements This work was partly supported by a Grant-in-Aid for Scientific Research on Priority Areas (No. 14078224, "Reaction Control of Dynamic Complexes")

15. Homo- and Copofymerization qfl-Hexene with Ethylene

101

from the Ministry of Education, Culture, Sports, Science and Technology of Japan. References and Notes [1] (a) H. H. Brintzinger, D. Fischer, R. Mulhaupt, B. Rieger, R. M. Waymouth, Angew. Chem. Int. Ed. 34 (1995) 1143-1170. (b) A. L. MeKnight, R. M. Waymouth, Chem. Rev. 98 (1998) 2587-2598. (c) G. W. Coates, Chem. Rev. 100 (2000) 1223-1252. (d) G. W. Coates, P. D. Hustad, S. Reinartz, Angew. Chem. Int. Ed. 41 (2002) 2236-2257. (e) V, C. Gibson, S. K, Spitzmesser, Chem. Rev, 103 (2003) 283-315. [2] (a) C. J. Schaverien, Adv. Organomet. Chem. 36 (1994) 283-362. (b) F. T. Edelmann, In; Comprehensive Organometallic Chemistry II (Edited by E. W. Abel, F. G. A. Stone, G. Wilkinson, M. F. Lappert), Pergamon, Oxford, 1995, Vol. 4, pp. 11-212. (c) H. Schumann, J. A. Meese-Marktscheffel, L. Esser, Chem. Rev. 95 (1995) 865-986. (d) R. Anwander, In Applied Homogeneous Catalysis with Organometallic Compounds, (Edited by B. Cornils, W. A. Hermann), VCH, Weinheim, 1996, Vol. 2, pp. 866-892. (e) M. Ephritikhine, Chem. Rev. 97 (1997) 2193-2242. (f) H. Yasuda, E. lhara, Bull. Chem. Soc. Jpn. 70 (1997) 1745-1767. (g) Z. Hou, Y. Wakatsuki, In Science of Synthesis (Edited by R. Noyori, T. Imamoto), Thieme, Stuttgart, 2002, Vol. 2, pp. 849-942. (h) Z. Hou, Y. Wakatsuki, J. Organomet. Chem. 647 (2002) 61-70. [3] (a) Z. M. Hou, Y. Wakatsuki, Coord. Chem. Rev, 231 (2002) 1-22. (b) W. E. Piers, D. J. H. Emslie, Coord. Chem. Rev. 233-234 (2002) 131155. (c) S. Arndt, J. Okuda, Chem. Rev. 102 (2002) 1953-1976. (d) J. Okuda, Dalton Trans. (2003) 2367-2378. (e) Z. Hou, Bull. Chem. Soc. Jpn. 76 (2003) 2253-2266. (f) J. Gromada, J. F. Carpentier, A. Mortreux, Coord. Chem. Rev. 248 (2004) 397-410. (g) Y. Nakayama, H. J. Yasuda, Organomet. Chem. 689 (2004) 4489-4498. (h) S. Arndt, J. Okuda, Adv. Synth. Catal. 347 (2005) 339-354. (i) Z. Hou, J. Synth. Org. Chem. Jpn. 63 (2005) 1124-1136. (j) Z. Hou, Y. Luo, X. Li, J. Organomet, Chem. in press. [4] (a) For examples of polymerization and oligomerization of a-olefins catalyzed by neutral organo rare earth metal complexes, see: G. Jeske, L. E. Schock, P. N. Swepston, H. Schumann, T, J, Marks, J. Am, Chem, Soc. 107 (1985)8103-8110.

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15. Homo- and Capotymerizatian of l-Hexene with Ethylene

103

[7] (a) For examples of polymerization catalysts based on cationic rare earth metal alkyl species bearing non-cyclopentadienyl ligands, see; B. D. Ward, S. Bellemin-Lapormaz, L. H. Gade, Angew. Chem., Int. Ed. 44 (2005) 16681671. (b) C. S. Tredget, F. Bonnet, A. R. Cowley, P. Mountford, Chem. Commun. (2005) 3301-3303. (c) S. Amdt, K. Beckerle, P. M. Zeimentz, T. P. Spaniol, J. Okuda, Angew, Chem. Int. Ed. 44(2005) 7473-7477. (d) S, Bambirra, M. W. Bouwkamp, A. Meetsma, B. Hessen, J. Am, Chem, Soc 126(2004) 9182-9183. (e) S. Arndt, T. P. Spaniol, J. Okuda, Angew. Chem., Int. Ed. 42 (2003) 5075-5079. (!) S. C. Lawrence, B. D. Ward, S. R. Dubberley, C. M. Kozak, P. Mountford, Chem. Commun. (2003) 2880-2881. (g) P. G. Hayes, W. E. Piers, R. McDonald, J. Am. Chem. Soc. 124 (2002) 2132-2133. (h) S. Bambirra, D. van Leusen, A. Meetsma, B. Hessen, J. H. Teuben, Chem. Commun. (2001) 637-638. (i) S. Hajela, W. P. Schaefer, J. E. Bercaw, J. Organomet. Chem. 532(1997) 45-53. [8] During the preparation of this work, homopolymerization of 1-hexene catalyzed by di-cationic scandium alkyl species was reported independently by Gade [7a] and Mountford [7b]. Copolymerization of ethylene with an otolefin by a cationic rare earth metal species has not been reported previously. [9] (a) For examples of copolymerization of ethylene with 1-hexene catalyzed by group 4 metal catalysts, see: K. Nomura,; K. Oya,; Y. Imanishi, J. Mol. Catal. A: Chem. 174 (2001) 127-140. (b) T. N. Choo, R. M. Waymouth, J. Am. Chem. Soc. 124 (2002) 4188-4189. (c) J. Huang, B. Lian, Y. Qian, W. Zhou, W. Chen, G. Zheng, Macromolecules 35 (2002) 4871-4874. (d) I. Bruaseth, E. Rytter, Macromolecules 36 (2003) 3026-3034. (e) M. Dankova, R. M. Waymouth, Macromolecules 36 (2003) 3815-3820. (f) M, K, Mahanthappa, A. P. Cole, R. M. Waymouth, Macromolecules 23 (2004) 836-845. (g) W. Q. Hu, X. L. Sun, C. Wang, Y. Gao, Y. Tang, L. P. Shi, W. Xia, J. Sun, H. L. Dai,; X. Q. Li, X. L. Yao, X. R. Wang, Organometallics 23 (2004) 1684-1688. (h) S. E. Reybuck, R. M. Waymouth, Macromolecules 37 (2004) 2342-2347. (i) R. Furayama, M. Mitani, J. Mohri, R. Mori, H. Tanaka, T. Fujita, Macromolecules 38 (2005) 1546-1552. [10] D. Cui, M. Nishiura, Z. Hou, Macromolecules 38 (2005) 4089-4095.

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[11] O. Tardif, M, Nishiura, Z. Hou, Organometallics 22 (2003) 1171-1173. [12]L. Resconi, F. Piemontesi, G. Franciscono, L. Abis, T, Fiorani, J. Am. Chem. Soc. 114(1992)1025-1032. [13] Homogeneous polymerization catalyst systems usually show no or negative "comonomer effect" in the copolymerization of ethylene with a-olefins, although positive "comonomer effect" was known in heterogeneous ZieglerNatta catalysis. For examples, see: J. C. W. Chien, T. Nozaki, J. Polym. ScL, Part A: Polym. Chem. 31 (1993) 227-237. See also ref. [14]. [14] L. J. Irwin, J. H. Reibenspies, S. A. Miller, J. Am. Chem. Soc. 126 (2004) 16716-16717. [15] (a) E. T. Hsieh, J. C. Randall, Macromolecules 15 (1982) 1402-1406. (b) W. X. Liu, D. G. Ray in, P. L. Rinaldi, Macromolecules 32 (1999) 38173819.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

105

16 Stereoerrors Formation in the Polymerization of Deuterated Propylene Victoria Vollds, Anatoli Lisovskii and Moris S. Eisen* Department of Chemistry and Institute of Catalysis Science and Technology, Technion Israel Institute of Technology Haifa 32000 Israel

Abstract The influence of the number of ancillary ligations and the corresponding structural features of three titanium benzamidinate complexes 1-3, in the polymerization of propylene, has been investigated. These complexes produce similar polymers indicating the formation of similar active species. The activation process was followed via 29Si-NMR spectroscopy. 1. INTRODUCTION The polymerization of propylene by single site catalyst has experienced a phenomenal growth in the last two decades, from academic to industrial research groups engaged in the design of new coordinative unsaturated catalysts for the controlled polymerization [1, 2]. The flourishing application of the "well-defined" single-site group 3 and 4 metallocene catalysts for the polymerization of a-olefins [3], together with sophisticated investigations on the role of the ligands composition and structure in the stabilization of the active centers in the mechanism for the activation of these metallocene catalysts has facilitated the search of the non-metallocene systems as alternative catalysts for this polymerization processes [4]. Among the various organometallic compounds synthesized during the last decade, the complexes of early transition metals with the bidentate JVjJV'-feftrimethylsilyl) benzamidinate ligations [TJRC(NR') 2 r (where R = C6H5 or substituted phenyls, R' = alkyl, aryl or SiMe3) have been widely described as promising alternative to the cyclopentadienyl

106

V. Volkisetal

complexes [5, 6]. The catalytic properties of several group 4 benzamidinate complexes in the polymerization of a-olefins have been previously investigated [7, 8]. 2. RESULTS AND DISCUSSION Our main goal was to investigate the influence of the compositional and structural features of the benzamidinate- titanium complexes 1, 2 and 3, having a similar chemical nature, but differing by the space symmetry and number of the ligations around the metal center, on their polymerization activity. Complexes 1-3 activated with MAO were found to be active in the polymerization of propylene only at high pressure, producing an elastomeric polypropylene with a wide polydispersity, as shown in Table 1.

Table 1. High pressure propylene polymerization results for complexes 1-3. yield of activity0 properties of polypropylene polymer mwdd Mw mtntnm 5 A-10" % 9 complex 1 1 0.043 16.0 500 CH2CI2 0.20 51000 2.83 12.8 0.40 2 1000 16.0 1.93 47000 3.13 14.9 3 2000 0.84 CHZCIZ 17.0 4.28 29000 5.81 15.7 1000 4 toluene 0.69 16.0 3.23 59000 3.70 10.9 Comdex 2 0.24 3.20 34.1 500 CHZCIZ 1.69 5 23.9 80000 6 0.38 1000 GH2GI2 3.10 25.1 51000 3.76 20.6 7 0.71 18.4 2000 CH2CI2 5.31 25.1 38000 6.33 1000 4.73 8 toluene 11.9 25.1 58000 3.97 0.63 complex 3 0.38 1000 9 2.30 GHzCIz 14.7 20.4 55000 3.77 1000 3.37 0.55 10 toluene 9.9 20.4 62000 3.26 1 23°C, 10.2 atrn, 6 ml of solvent, 40 ml C3H6,180 mm; mol Ti x 10: g PP x mol Ti"1 x h"1;d molecular weight distribution. entry

process conditions8 solvent eatb AI:Ti ratio

16. Sterreoerrors Formation in the Polymerization afDeutemtedPropylem

107

As may he seen, at AhTi ratios greater than 500, the polymerization activities of the complexes in each solvent differs insignificantly. These results induce us to consider that possible similar active species are operative in the polymerization process regardless of the starting materials. For all the complexes, the elastomeric polypropylene produced in toluene has somewhat higher molecular weight than the polymers formed in dichloromethane. Raising the MAO concentration in the catalytic mixture decreases the molecular weights of the polymers and increases their molecular weight distribution. This result normally indicates that the aluminum transfer chain termination mechanism is operative inducing the lower molecular weights. However, according to the 13C NMR analysis of the end groups of the polymers, the chain termination was found to be (3-hydrogen elimination. Taking into consideration that the resulted polymers have a wide MWD, which increases with an increasing of Ti:Al ratio, the assistance of MAO in the formation of different active species from pre-catalysts 1-3 may be assumed. Interestingly, in spite of the different structural features of the used precatalysts, the molecular weights of the polymers created under the same conditions, were unexpectedly found to be alike. As regards to the stereoregularity of the monomer insertion, the isotacticities of the polymers are also similar, although a slight increase in the mmmm of the polymer only produced by complex 2 in CH2C12 is observed. The high polydispersity of the obtained polypropylenes is a consequence of the presence of various active species producing polymers with a wide spectrum of molecular weights and different tacticities. Such polymers can be fractionalized in hexane into a solid hexane-insoluble (HI), and elastomer hexane-soluble (HS) fractions, and the representative results for complexes 1 and 2 are given in Table 2. Table 2. Results of the fractionalization for polymers PP1 and PP2 produced by complexes 1 and 2 correspondingly in hexane.

samples PP1 (whole) PP1-HS PP1-HI PP2 (whole) PP2-HS PP2-HI

%wt 100 98.2 1.8 100 96.7 3.3

M« 59000 55000 238000 58000 56000 216000

mwd 3.1 3.2 3.3 3.8 3.1 3.6

mmmm, % 10.9 10.0 74.4 11.9 10.0 74.5

Interestingly, the major part (97-98%) of the polypropylenes PP1 and PP2 were the soluble hexane fraction obtained as an elastomeric (not atactic) polymer. For each of the polymers, in each fraction the molecular weights and isotacticities of the polymers were found to be unexpectedly identical Property-

108

V.VoMsetal.

wise, the hexane soluble elastomers were found to be closed by its tacticities to the elastomers described by Resconi [9]. However, the MW was noticeably lower. One possible reason for the elastomeric behavior of such low tacticity and low MW polymers is the presence of comparatively large amounts of ethane and butane fragments, formed as the result of misinsertions. The hexane insoluble solids were high molecular weight polymers with larger isotacticities. To shed some light on the mechanism for the formation of elastomeric polypropylene by different benzamidinate complexes, it was necessary to clarify two conceptual questions: how the different fractions are formed and how the elastomeric fraction is produced It seems that during the polymerization process, the complexes undergo rearrangements, forming similar number of structural alike species proposed to be active for the polymerization. To corroborate this hypothesis, one of such active species was postulated to be the corresponding Al benzamidinate that can be formed as a result of interaction of the studied Ti benzamidinates with methylalumoxane. To confirm experimentally such supposition, the aluminum benzamidinate complexes [Ti-C6H5-C(NSiMe3)2AlX2] (X = Cl (4), Me (5)), were synthesized by the reaction of the lithium benzamidinate ligand [ri-CfiHsC(NSiMe3)2Li] with AICI3 or the reaction of the neutral benzamidinate ligand [C6H5-C(=NSiMe3)(NSiMe3)2] with AlMe3, correspondingly. We have investigated the features of activation of complexes 1 and 2 with methylalumoxane using the 29Si NMR technique allowing discriminating various species formed on different steps of the activation. The spectra obtained were compared to the spectrum of Al benzamidinates 4 and 5 taken as a reference. Figure 1 illustrates the monitoring of the activation of complex 1. The spectrum (a) is of the pure complex 1 whereas spectrum (b) is of complex 1 activated with MAO. One of the signals in spectrum (b) matches the signals in the spectra (c) for Al benzamidinate dichloride 4 and (d) for Al benzamidinate dimethyl 5. A similar result was obtained for complex 2. These results indicate that upon the reaction of either complex 1 or 2 with MAO, the monobenzamidinate aluminium complex is obtained. The formation of the aluminium complex involves the metathesis of the benzamidinate ligand from Ti to Al. The activities in the polymerization reaction of complexes 4 and 5 at high propylene pressure were found to be about 10 times lower as for the corresponding titanium precatalysts 1 and 2 (~ 0.5 x 104 g PP x mol Al"1 x h"1) producing an atactic polymer, therefore not being the major player in the polymerization process. The formation of two additional signals (Figure lb) is representative of two different complexes, each of one probably responsible for the different fraction. If we assume that the formation of a bis(benzamidinate) titanium methyl complex with a C^-symmetry is responsible for the small isotactic fraction, a second monomeric mono(benzamidinate) titanium complex

16. Sterreoerrors Formation in the Polymerization of Deuterated Propylene

109

must be responsible for the formation of the elastomeric polymer. Hence, complexes 1 and 2 rearranges upon their reaction with MAO, Plausible mechanism for the rearrangement of complex 2 is described in Scheme 1.

.

It

1:

L2

]L

11

13

1!

LI

ID

13

B

II

II

3

1

t

^

S

7

I

T

s

! !

s

i

1 2

t

I

3

4

1

2

I

1

c

-1

-1

-3

1

I

-1

-»

-3

1

d

-J

- 1 - S - 4 mrr

1

I

-1

-2

-1

- * wrr

-1 in

Figure 1, Si NMR monitoring of the aetive specie formation from complex 1 in toluene-' complex 1, b — complex 1 + MAO at Ti:A 1 ratio 1:20, c — complex, 4, d — complex 5,

Hexane soluble elastomer

He&ane Insoluble f

Scheme 1. Plausible scheme for the rearrangement of complex 2.

110

V, Valkisetal

As regarding to the elastomeric behavior of the polymers produced by benzamidinate complexes, which is related to the stereoregularity of the polymer, it is usually considered to be a result of the two competing reactions: a) stereoregular polymerization inducing isotactic material, b) an intramolecular epimerization of the growing polymer chain that induces stereo-errors. For the latter two possible epimerization mechanisms have been reported: the first one proposed by Busico [10,11] leads to the formation of single errors in the polymer chain; the second mechanism proposed by Resconi [12] includes in addition, the formation of exo-double bonds at the polymer chain and particular chain-ends. To discriminate between the two possible pathways, the polymerization was carried out with 2-D-propene at low and high pressures and compared to the polymerizations with non-labelled propene. The polymerization data is presented in Table 3. Table 3 indicates three unexpected effects. First, the rate of insertions is much faster for the polymerization with deuterated propylene. This inverse isotopic effect rests on the fact that deuterium is an electron releasing atom as compared to hydrogen. Second, there is a trend of higher isotacticity for the deuterated polymers relatively to non-deuterated analogs. We presumably could assume here better stereoselective interactions for the incoming deuterated monomer as compared to its non-deuterated analog. Finally, larger MW are obtained for the deuterated polypropylene as comparing to the non-deuterated. We have found that the use of the deuterated substrate leads to increasing of both rates of insertions and terminations, but the effect on the rate of insertions was measure to be stronger than on the rate of terminations. Table 3. Results of the polymerization of deuterated and non-deuterated propylene catalyzed by benzamidinate complexes Run

Cat

Substrate

Pressure atm

Time h

Activity"

Mw xlQ" 3

MWD C

mmmm , %

1

1

H2C=CD-CH3

1.5-2.0

22

0.58

99000

1.77

12.5

2

1

H2C=CH-CH3

1.5-2.0

22

0.26

8B000

2.26

9.4

3

1

H2C=CD-CH3

9.0

3

0.54

143000

1.70

58.9

4

1

H2C=CH-CH3

9.0

3

0.48

19000

2.48

10.9

a Ti:Al = 1:800, 3 ml of toluene, 5 mg catalyst; distribution Mw/Mn; d isotactic pentad content.

g PP- mol Ti~l- h"l;

c

molecular weight

In order to clarify the pathways for the possible formation of stereoerrors during the polymerization, the 13C{2H}-NMR shows no deuterium incorporation into the methyl group (Busico or Resconi epimerization

16. Sterreoerrors Formation in the Polymerization ofDeuteratedPropylene

111

pathways). However we have observed a deuterium-hydrogen exchange between -CD- and -CH 2 - groups, given -CH- and -CHD- fragments on the skeleton chain. This exchange can be explained by the mechanism, presented on Scheme 2,

Ti reinsertion

fS-D elimination

reinsertion

y-H elimination

D-reinsertion

H-reinsertion

j-D

elimination

I

Scheme 2. The exchange of CH(CH3)- and CF^-hydrogens

3. CONCLUSIONS Here we have presented a totally new epimerization pathway for the formation of stereoerrors using octahedral complexes in the polymerization of propylene.

Acknowledgment!. This research was supported by the Israel- USA Binational Science Foundation under Contract 2004075. Reference! [1] W. Kaminsky, In: Advances in Catalysis; eds: B. C. Gate, H. KnSzinger,; Academic Press: San Diego, 46 (2002) 89, [2] P. Corradini, J. Polym. Sci., Part A: Poly. Chem. 42(3) (2004) 391. [3] H. G, Alt, A. Kfippl. Chem. Rev. 100 (2000) 1205, and references therein. [4] V. C. Gibson, S. K. Spitzmesse, Chem. Rev. 103 (2003) 283. [5] F. T. Edelmann, Coord. Chem. Rev. 137 (1994) 403, and references therein. [6] K. C. Jayarante, L. R. Sita, J. Am. Chem. Soc. 123 (2001) 10754. [7] J. C. Flores, J. C. W. Chien, M. D. Rausch, Organometallics 14 (1995) 1827. [8] (a) D. Herscovics-Korine, M. S. Eisen, J. Organomet. Chem. 503 (1995) 307. (b) V. Yolkis, E. Nelkenbaum, A. Lisovskii, G. Hasson, R. Semiat,

112

Y.VoMsetaL

M. Kapon, M. Botushansky, Y. Eishen, M. S. Eisen J. Am. Chem. Soc, 125 (2003) 2179. [9] L. Resconi, R. L. Jones, A. L. Rheigold, Organometallics, 15 (1996) 998. [10] V. Busico, R. Cipullo, J. Am. Chem. Soc. 116 (1994) 9329. [11] V. Busico, L. Caporaso, R. Cipullo, L. Landriani, J. Am. Chem. Soc. 118 (1996), 2105, [12] L. Resconi, J. of Mol. Catal, A: Chemical 146 (1999) 167.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

113 113

17 Vinylic Polymerization of Norbornene with Neutral Nickel(II) Complexes Bearing p-Diketiminato Chelate Ligands Yi-Qun Duan, Xiao-Fang Li, Yue-Sheng Li* State Key Laboratory of Polymer Physics and Chemistry, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, China, and Graduate School of the Chinese Academy of Sciences

Abstract A series of neutral nickel(II) complexes la-c bearing asymmetric bidentate Pdiketiminato ligands have been investigated as catalysts for vinyl-addition polymerization of norbornene (NBE) in the presence of modified methylaluminoxane (MMAO) cocatalyst. The highest catalytic activity up to 4.5 lxl0 4 kg FNBE/mol-Ni-h and viscosity-average molecular weight (Mv) of polymers up to 1,07x106 g/mol were observed under optimal conditions, and lac exhibited higher catalytic activities, afforded higher molecular weight polymers than the corresponding bis(P-diketiminato)mekel(II) complexes, 2a-c. 1. INTRODUCTION The research on the vinyl-addition polymerization of norbornene (NBE), which emerges with the exploitation of Ziegler-Natta catalysts since 1950's [1,2], has been greatly developed with the upsurge of metallocene-MAO based catalysts in the field of transition-metal-catalyzed olefin polymerization [3-6]. Unlike ring-opening metathesis and cationic or radical polymerization, the vinyladdition polymerization yields PNBE as a saturated polymer with the bicyclic structure of the monomer left intact [7]. This unique microstructure gifts the PNBEs with many excellent physical properties, such as high density, high glass-transition temperature, corrosion resistance, optical transparency, low

114

Y.-Q. Duan et al.

birefringence and dielectric properties, which has attracted increasing attention from both of the academic and industrial world [8,9], Besides the zirconocene catalysts for the vinyl-addition polymerization of NBE originally introduced by Kaminsky, late transition metal such as nickel [10-16], cobalt [17-19] and palladium [20-28] catalysts have also been developed to catalyze the polymerization of NBE with much higher catalytic activity. Compared with the highly stereo-regular PNBEs produced by zirconocene catalysts, which do not appear to dissolve in any organic solvent [9], the amorphous PNBEs obtained with late transition metal catalysts own good solubility especially in aromatic halide, which indicates their unique potential in solution-processing. In 2000, Grubbs reported the potential application of neutral Ni complexes bearing salicylaldiminato ligands to catalyze the copolymerization of ethylene and NBE derivatives, while detailed catalytic data for NBE homopolymerization were not given [29]. Later, we found that Grubbs' neutral nickel catalysts activated with modified methylaluminoxane (MMAO) were a powerful catalytic system for the vinyl-addition polymerization of NBE, producing high molecular weight and amorphous PNBEs with good thermal stability [30]. Recently, our exploration on bis(P-diketiminato)nickel(II) complexes revealed that this series of catalysts also were efficient for the NBE polymerization and can be easily modified by varing substituents on the complex backbones [31]. We wonder if the neutral Ni(II) complexes bearing single P-diketiminato ligands are more active towards vinyl-addition polymerization of NBE and produce higher molecular weight polymers. Here we report NBE polymerization behaviors of a series of the neutral mckel(II) catalysts with P-diketiminato ligands activated with MMAO under mild conditions. Further 13C NMR spectra suggested the vinyl addition nature of the produced PNBEs, in which no ring-opened product was observed. 2. EXPERIMENTAL Materials. The details of synthesis and characterization of the catalysts la-c (Scheme 1) have been reported elsewhere [32]. NBE was dried over sodium, vacuum-transferred, and degassed by repeated freeze-pump-thaw cycles, oC6D4CI2 was obtained from Aldrich and used without further purification. Modified methylaluminoxane (MMAO, 7% Al in heptane solution) was purchased from Akzo Nobel Chemical Inc. Polymerization Procedure. All work involving air and moisture sensitive compounds was carried out using standard Schlenk techniques. 2.0 ml of a fresh catalyst solution (chlorobenzene, 0.5 pjnol catalyst), 3.0 ml of NBE in chlorobenzene, and 14.0 ml of chlorobenzene were added under inert gas

17. Vinylie Polymerization ofNorbornene with Neutral Ni (II) Complexes

115

atmosphere into a Schlenk flask with a mechanical stirrer. The reaction was started by the addition of 0,5 ml of a MMAO solution (1.0 mmol in heptane) at 30 °C. Total reaction volume was 20 ml, unless otherwise stated. This was achieved by the variation of the amount of chlorobenzene if necessary. After 5 min, the reaction mixture was poured into 200 ml of acidic ethanol (ethanol/HClcorre = 50/1). The polymer was isolated by filtration, washed with methanol, and vacuum dried at 80°C for 24 h. Analytical Procedures. NMR analyses of polymers were performed on a Varian Unity 400 MHz spectrometer at 135°C, using o-C6D4Cl2 as solvent. DSC measurements were performed with a Perkin-Elmer Pyris 1 Differential Scanning Calorimeter. Viscosity-average molecular weights (Ms) were calculated from the intrinsic viscosity by using the Mark-Houwink coefficients: a = 0.56, K= 5.97X10"4 dyg [33]. 3. RESULTS AND DISCUSSION Preliminary research in our group had indicated that single component bis(chelate) Ni(II) complexes were not able to polymerize NBE without MMAO as a cocatalyst [31]. In this research, the neutral nickel(II) complexes la-c, bearing the single corresponding ligands were also found to be inefficient for NBE polymerization in the absence of MMAO, with trace polymer obtained. However, when subsequent experiments were carried out in the presence of MMAO, all of the nickel(II) complexes la-c exhibited high catalytic activity for the NBE polymerization.

a:

R i =Ph,R 2 =CF 3

b: R,= Ph, R2= CH3

^ \__

c: R,= CF3> R2= CHS

la-c

2a-c

Scheme 1. Nickel(II) complexes la-c and 2a-c

The ratio of MMAO/la, which is expressed as Al/Ni molar ratio here, has significant effects on polymer yields, catalytic activities and the molecular trace weights of the polymers obtained. In the absence of MMAO, a trace amount of polymer could be obtained. However, as shown in Figure 1, with the increase of the Al/Ni molar ratio at a constant Ni concentration, polymer yield gradually increased. Within 5 min polymerization, PNBE yield rised up to 93.6% at the

Y.-Q, Duan et al.

116

Al/Ni ratio of 3000/1; the yield of PNBE could reach up to 99.8% upon the further increase in the Al/Ni molar ratio (5000/1). It is interesting to note that 12 100 100Yield after an initial ascent with the M increase of Al/Ni ratio from 500 90 10 to 2000, Mv of PNBE increased up 6 80 to a summit of l.OlxlO g/mol, then began to decrease upon the 70 8 continued increase of Al/Ni ratio, 60 6 and finally reached to 0.56x10 50 g/mol. The subsequent decrease 6 of My is probably due to the faster 40 chain transfer reaction to Al 0 1000 2000 3000 4000 5000 compounds than the chain AIM Al/Ni (molar ratio) propagation reaction, when Al/Ni Figure 1. Plot of yield and Mv versus Al/Ni ratio exceeded 2000. (molar ratio). 0.50 ^mol la, 1.88 g NBE, V M = Sufficient reaction time 20 ml, polymerization reaction at 30°C for 5 min. assured the high yield of PNBE, As shown in Figure 2, initial yield of polymer was only 80.9% in 5 min, but 120 the yield of PNBE kept increasing, 100 and reaches up to 99.8% in 120 min. 80 Reaction temperature also had 60 considerable effects on both the 40 catalytic activity and molecular 20 weights of polymers. 0 As shown in Figure 3, nickel(II) 5 min 30 min min 120 120 min mm min complex la exhibits high activity of 2.47X104 kg PNBE/mol-Ni-h at 0°C, Yield(%) Yield % Mv Mv (10000 10000 g/mol) g/mol and the catalytic activity reached to 3.67x104 kg PNBE/mol-Ni-h at 50°C. Figure 2, Plot of reaction time vs. PNBE yield. The activity slightly decreased but still 0.50 |X mol la, 1.88 g NBE, V t^, = 20 ml, remains at 3.42x10 kg PNBE/mol- Al/Ni = 2000, 30°C. Ni-h at 70°C. Nevertheless, for the corresponding bis(chelate) Ni(II) complexes, the activity increases to a summit around 20 °C, but decreased dramatically with ascending temperature and finally drops down at the lowest value at 50 °C [31]. Therefore, compared with the corresponding bis(chelate) complexes, nickel(II) complexes la-c bearing single P-diketiminato ligands proved to be robust catalysts for the NBE polymerization at high temperature, which indicates their potential as excellent catalysts for NBE polymerization. (Mv (106 g/mol)

Yield (%)

v

17. Vinylic Polymerization ofNorbomene with Neutral Ni (11} Complexes

117

Mv (105 g/mol)

Activity (104 kg PNBE/molNih)

In contrast, reaction temperature 3.8 12 influences molecular weights of 3.6 polymers in a different style. No Activity 10 distinct changes of the molecular 3.4 Mv weight for the resultant PNBE was 3.2 8 observed between 0 and 30 °C, but the 3.0 Mv value notably decreased upon increasing the temperature till 70 °C: 2.8 6 Mv value became half from 30 to 70 °C. 2.6 This may be due to the fact that fast 4 2.4 chain propagation, indicated by the high catalytic activity, is always 23 30 4 40 -10 0 10 20 0 50 60 70 80 o Q Temperature ( C) accompanied by faster chain transfer reaction, finally leading to the decrease Figure 3. Plot of activity and M vs. reaction v of molecular weight of polymers. temperature. 0.50 |imol la, 1.88gNE, Ftatai= To understand a relationship 20 ml, Al/Ni=2000, polymerization, for 5 min. between structures of the complexes la-e and catalytic activities and molecular weights of PNBE, corresponding data were tested and summarized in Table 1. Generally, catalyst performances are influenced in the way of both steric hindrance and electronic effect. As it is well known, steric hindrance that bulky substituents bring into late transition metal catalyzed polymerization system is propitious to control chain transfer reaction and increase the molecular weight of polymers. Compared with the other complexes, catalyst la, with a phenyl group and a CF3 group both as bulky substituents, produces PNBE with the highest molecular weight, 10.7x105 g/mol, while complex lc, bearing a CH3 group and a CF3 group, produces PNBE with the lowest Mv, 5.6xlO5 g/mol. Complex l b supported by a CH3 group and a phenyl group polymerizes NBE with a medium Mv of 7.5x10s g/mol. On the other hand, electronic effect of different substituents plays an important role in adjusting catalytic activities of Ni(II) complexes polymerization system. As seen from Table 1, complex l b , with a phenyl group and CH3 group as electron donating substituents, polymerizes NBE with the lowest activity (1.06 xl04kgPNBE/mol-Ni-h); while complex lc, bearing a CF3 group and a CH3 group, owns higher catalytic activity (2.11xl04kgPNBE/ mol-Ni-h). This indicates that CF3 group with stronger electron-withdrawing ability than the phenyl group could efficiently mcrease catalytic activities of single chelate (3-diketiminato nickel(II) complexes towards NBE polymerization, which acts in the same fashion of the corresponding bis(chelate) nickel(II) complexes [31]. Noticeably, complex la, with a phenyl group and a CF3 group, exhibited the highest activity for NBE polymerization up to 3.65x104 kg PNBE/

Table 1, The results of the vinyl-addition polymerization of norbomenea Entry

AI/Ni

Norbomene

(mol ratio) -

(g) 1,88

la

soo

la la

1000

1.88 1.88

ib

la

2 3 4 5 6

la

1500 2000

la

3000

7 8

Temperature

(min)

fC)

60 5

30 30 30

1.88

5

30

1.88 1.88

5 5

30 30

1.SS 1.88

la

5000

9

2000 2000

10

la

2000

11

la la

2000

1.88

lb

2000 2000

1.88 1.88

lc 2a"

2000

IS

2500

16 17

»' 2c*

2S00 2S00

14

Time

5

la la

12 13

a

Catalyst

Polymer

Yield (%) .

Activity 4

(10 kgPNBE/mol-M-h) -

(lO'gm -

(B) trace 0.771

41.0

1.85

0.889 1.401

47.3 74.S

2,14

9,5

3.36

10.

1.521 1.760 1.876 1.720

80.9 93.6

3,65 4.22

10. 8.1

99.8

4.51

91.5 99.8 54.8

0.23 0,19 2.47

5.6 5.8

7.7

5

30

30 120

30 30

5 5

0 SO

1.530

81.4

3.67

10. 6.2

5 5

70 30

1.350 0.440

71.8 234

3.42 1.06

3.7 7.5

1.88

5

30

0.880

5.6

15

30

0.S90

46.8 98

2.11

0.6 0,6 0.6

15 15

30 30

0,350 0.580

$8 97

1.18 0.70 1.16

5.5 6.4

1.S8 1.88

1,876 1.030

6.7

5.9

0.5/flnol of nickel complex, Vum — 2Qml (ehlorabenzene). b NBE polymerization with complex a as a single component E0.2/ffnol of nickel complex, Ktmai — 15ml polymerization reaction for 15 min at 30 °C. For polymerization data of entry 16 and 17, see [32].

17. Vinytic Polymerization ofNorbornene with Neutral Ni (II) Complexes

119

mol-Ni-h. Typically, bulky substituents always go against inserting olefin into metal-carbon bonding, which decreases the rate of polymerization and hence the catalytic activity. But why complex la, with much steric hindrance possesses higher activity than complex lc? This may be due to the fact that the phenyl group is not only a bulky substituent, but also an electron-withdrawing group. So when electronic effect acts as the leading factor for polymerization activities, phenyl group could increase catalytic activities more than CH3 group, although the latter possesses smaller hindrance for olefin insertion. Interestingly, comparing with the corresponding bis(chelate)complexes, the single chelate Ni(II) complexes la-c all exhibited higher activities towards NBE polymerization (3.65, 1.06 and 2.11xl0 4 kg PNBE/mol-Ni-h vs 1.18, 0.7 and 1.16xl0 4 kg PNBE/mol-Ni-h, Table 1). To explain this phenomena, possible mechanism for NBE polymerization catalyzed by Ni(II) complexes bearing single or bis(p-diketiminato) ligands is supposed as shown in Scheme 2. For nickel (II) complexes la-c with single chelate ligands, the function of MAO as a cocatalyst is to withdraw the PPh3 ligand and generate a three coordinating neutral complex la'-c' occupied by the N, O atoms and a phenyl group, with a coordination vacancy left for the further coordination of NBE monomer and the enchainment of coordinating monomers. Then this initial active site is transferred into the three coordinating neutral complex a"-c"as major active centers of polymerization [34].

2a-c

2a'-c'

3a-c

Scheme 2. Proposed Mechanism for vinyl-addition polymerization of NBE.

However, for the bis(P~diketiminato)Ni(II) complex 2a-c, one MAO can only snatch one (p-diketiminato) ligand from the original complex, in order to form a three coordinating neutral complex a"-c" as an active center. Since the resulted Al complex 3a-c with one chelate ligand may not be stable as MAO, this MAO snatching [NO] ligand reaction could be reversible. Then only part of the initial complexes could be transformed into active Ni centers (a"-c") for

Y.-Q, Duan et al.

120

polymerization by MAO and the number of the latter would be much fewer, which finally leads to the lower catalytic activity of bis(chelate) complexes than the corresponding single chelate catalysts. 13 C NMR spectrum of typical PNBE obtained by complex la (Entry 5) is presented in Figure 4. Resultant polymer is vinyl addition in nature since no olefinic resonances are observed in the isolated polymer (e.g., no ROMP polymer was formed). Assignment of methylene and methine resonances are listed as follows, signals at 29.5-34.0 ppm are from carbon-5 and carbon-6; the ones at 35.3-37.5 ppm originate from carbon-7; the ones at 38.4-42.5 ppm are for carbon-1 and carbon-4; and the ones at 46.7-54.5 ppm are for carbon-2 and carbon-3. In addition, since the resonance in the 20-24 ppm region is considered as evidence of endo enchainment on the basis of model studies, the absence of such resonances in Figure 4 indicates the exo enchainment nature of the PNBE [35]. The 13C-NMR spectrum is similar to that reported by Greiner's and Wu's groups [36,37]. C1.C4 C7 C5, C6

C2,C3

HO

120

100

(?'c

60

JO

20

Figure 4. "C NMR spectra of PNBE recorded in o-CsD4Cl2 at 135°C

The r g 's of the PNBEs range from 360.1 to 415.8 °C, suggesting good thermal stability of the polymers. All polymers are soluble at room temperature in chlorobenzene and o-dichlorobenzene» which indicates low stereoregularity. 4. CONCLUSIONS Neutral nickel (II) complexes la-c bearing single (p-diketiminato) ligands activated with MMAO proved to be highly efficient catalysts for the vinyl addition NBE polymerization. Under optimal conditions, complex la exhibits the highest catalytic activity up to 4,5lxl 04 kg PNBE/mol-Ni-h and produces polymer with high viscosity-average molecular weight up to 1.07X106 g/mol. The catalytic activities, yield and molecular weight of polymers were adjusted effectively by Al/Ni ratio, reaction time, reaction temperature and the structure

17. Vinylic Polymerization of Narbarnme with Neutral Ni (1$ Complexes

121

of complexes, with steric effects and electron-withdrawing effects of substituents on the catalyst backbone. The PNBEs obtained here exhibit good thermal stability, are amorphous and soluble at room temperature in halogenated aromatic hydrocarbons, A discussion and comparison between performances of (p-diketiminato)Ni (II) complexes la-c and the corresponding Ms(ehelate) complexes 2a-e, derived from a serial experiments under similar conditions, were presented to help the understanding of NBE polymerization mechanism with neutral nickel (II) complexes bearing (p-diketiminato) ligands. References [1] G. Sarttori, F, C. Ciampelli, N. Cameli, Chim. Ind. (Milan) 45 (1963) 1478-1482 [2] T. Tsujino, T. Saegusa, J, Furukawa, Makromol. Chem. 85 (1965) 71-79. [3] W. Kaminsky, A. Noll, Polym. Bull. 31 (1993) 175-182. [4] W. Kaminsky, A. Bark, Polym. Int. 28 (1992) 251-253. [5] W. Kaminsky, A. Bark, R. Steiger, J. Mol. Catal. 74 (1992) 109-119. [6] M. Arndt, R. Engehausen, W. Kaminsky, K. Zoumis, J. Mol. Catal. A: Chemical 101 (1995) 171-178. [7] N. Seehof, Ch. Mehler, S. Braining, W. Risse, J. Mol. Catal. 76 (1992) 219-228. [8] C. Janiak, P.G. Lassahn, Macromol. Rapid Commun. 22 (2001) 479-493. [9] S. Ahmed, S. A. Bidstrup, P.A. Kohl, P. J. Ludovice, J. Phys. Chem. B 102 (1998) 9783-9790. [10] T. J. Deming, B. M. Novak, Macromolecules 26 (1993), 7089-7091. [11] W. Massa, N. Faza, H. C. Kang, C. Focke, W. Heitz, Acta. Polym. 48 (1997) 432-437. [12] M. Arndt, M. Gosmann, Polym. Bull. 41 (1998) 433-440. [13] F. Peruch, H. Cramail, A. Deffieux, Macromol. Chem. Phys. 199 (1998) 2221-2227. [14] C. Mast, M, Krieger, K. Dehnicke, A. Greiner, Macromol. Rapid. Commun. 20 (1999) 232-235. [15] S. Brorkar, P. K. Saxena, Polym. Bull. 44 (2000) 167-172. [16] D. Zhang, G. X. Jin, L. H. Weng, F. S. Wang, Organometallics 23 (2004) 3270-3275. [17] F. P. Alt, W. Heitz, Macromol. Chem. Phys. 199 (1998) 1951-1956. [18] F. P. Alt, W. Heitz, Acta. Polym. 49 (1998) 477-481. [19] F. Pelascini, F. Peruch, P. J. Lutz, M. Wesolek, J. Kress, Macromol. Rapid Commun. 24 (2003) 768-771.

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[20] C. Tanielian, A. Kiennemann, T. Osparpueu, Can. J. Chem. 57 (1979) 2022-2027. [21] A. Sen, T. W. Lai, R. R. Thomas, J. Organomet. Chem. 368 (1988) 567588. [22] C. Mehler, W. Risse, Macromolecules 25 (1992) 4226-4228. [23] T. F. A. Haselwander, W. Heitz, S. A. Krugel, J. H. Wendorff, Macromol. Chem. Phys, 197 (1996) 3435-3453. [24] B. S. Heinz, F. P. Alt, W. Heitz, Macromol. Rapid Commun. 19 (1998) 251-256, [25] A. S. Abu-Surrah, K. Lappalainen, T. Repo, M. Klinga, M. Leskela, H. A. Hodali, Polyhedron 19 (2000) 1601-1605. [26] A. S. Abu-Surrah, K. Lappalainen, M. Kettunen, T. Repo, M. Leskela, H. A. Hodali, B. Rieger, Macromol. Chem. Phys. 202 (2001) 599-603. [27] J. Lipian, R. A. Mimna, J. C. Fondran, D. Yandulov, R. A. Shick, B. L. Goodall, L. F. Rhodes, Macromolecules 35 (2002) 8969-8977. [28] P. G. Lassahn, V. Lozan, C, Janiak, J. Chem. Soc, Dalton Trans, (2003) 927-935. [29] T. R.Younkin, E. F. Connor, J. I. Henderson, S. K. Friedrich, R. H. Grubbs, D. A. Bansleben, Sciences 287 (2000) 460-463. [30] X. F. Li, Y. S. Li, J. Polym. Sci. Part A: Polym. Chem. 40 (2002) 26802685. [31] Y. Z. Zhu, J. Y. Liu, Y. S. Li, Y. J. Tong, J. Organomet. Chem. 689 (2004) 1295-1303. [32] X. F. Li, Y. G. Li, Y. S. Li, Y. X. Chen, N. H. Hu, Organometallics 24 (2005)2502-2510. [33] D. A. Barnes, G. M. Benedikt, B. L. Goodall, S. S. Huang, H. A. Kalamarides, S. Lenhard, L. H. Mclntosh, K. T. Selvy 111, R. A. Shick, L. F. Rhodes, Macromolecules 36 (2003) 2623-2632. [34] Corresponding aluminium complex bearing Ph and CH3 groups have been tested and proved to be inactive to catalyze NBE polymerization. [35] C. Mast, M. Krieger, K. Dehnicke, A. Greiner, Macromol. Rapid Commun. 20(1999)232-235. [36] Q. Wu, Y. Y. Lu, J. Polym. Sci. Part A: Chem. 40 (2002) 1421-1425. [37] T. F, A. Haselwander, W. Heitz, Macromol. Rapid Commun. 18 (1997) 689-697.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

123 123

18 Effect of Anionic Ancillary Ligand in Ethylene Polymerization Catalyzed by (Arylimido)vanadium Complexes Containing Aryloxide, Ketimide Ligand Kotohiro Nomura,*, Wei Wang, and Junji Yamada Graduate School of Materials Science, Nara Institute of Science and Technology, 89165 Takayama, Ikoma, Nara 630-0101, Japan

Abstract Factors affecting the catalytic activity in ethylene polymerization using (arylimido)vanadium dichloride complexes containing anionic ancillary donor ligand of the type, (ArN)VCl2(X) [X: O-2,6-Me2C6H3, O-lfi-^tzCsHi, N=C'Bu2, N=C('Bu)(CH2SiMe3)], have been explored. These complexes exhibited high catalytic activities in the presence of MAO cocatalyst and the activities at 25 °C by the aryloxide analogues were higher than those by the ketimide analogues. In contrast, the activities by the ketimide analogues (X = N=C'Bu2) increased at higher temperature (50 °C), whereas the significant decrease in the activities was observed by the aryloxide analogues. Although the aryloxide analogues showed especially high catalytic activities in the presence of EtaAlCl, the observed activities by the ketimide analogues in the presence of Et2AlCl were lower than those in the presence of MAO. 1. INTRODUCTION Topics concerning precise synthesis of polyolefins by new generation of transition metal catalysis attract considerable attention [1], because the evolution of new polyolefins that can not be prepared by ordinary catalysts is highly expected. Since the classical Ziegler type vanadium catalyst systems displayed the unique characteristics such as synthesis of high molecular weight polymer with narrow polydispersity, synthesis of ethylene/a-olefin copolymer with high a-olefm content, and others [2], therefore, the design of new

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vanadium complex catalyst for the controlled olefin polymerization has been one of the most attractive targets. We reported recently that (arylimido)(aryloxo)vanadium complexes of type, VCl2(^-2,6-Me2C6H3)(OAr) [Ar = 2,6-Me2C6H3 (1), Ifi-^C^ (2), Chart 1], exhibited high catalytic activities in ethylene polymerization [3,4], and the activities in the presence of Et2AlCl was higher than that in the presence of MAO [3,4]. We also demonstrated that these complexes are also effective for synthesis of ultra high molecular weight poly(ethylene-co-norbornene)s, and the norbornene incorporation as well as the Mn values were dependent upon the cocatalyst employed [4]. Since we recently reported the synthesis of various (arylimido)(ketimide)vanadium complexes of the type, VCl2(NAr')[N=C('Bu)R] [Ar' = 2,6-Me2C6H3 and R = (Bu (3), CH2SiMe3 (4); Ar' = 2,6s and R = 'Bu (5), Chart 1], and isolated a vanadium-alkylidene complex which showed remarkable catalytic activity for ring-opening ci metathesis polymerization of Cl norbornene [7], we thus studied these R3 complexes as the olefin coordination 3 R*;R = Me; f Bu <3), = Me(1).'Pr(2) Me;CH 2 SiMe 3 (4),'Pr;'Bu (5) polymerization catalyst precursors. 2. EXPERIMENTAL

Chart 1

All experiments were carried out under a nitrogen atmosphere in a Vacuum Atmospheres drybox unless otherwise specified. Anhydrous grade of toluene (Kanto Chemical Co., Inc.) was transferred into a bottle containing molecular sieves (mixture of 3A, 4A 1/16, and 13X) in the drybox, and was used without further purification. Et2AlCl solution in R-hexane (1.0 mol/L) was purchased from Kanto Chemical Co., Inc. and was used as received. Toluene and AlMe3 in the commercially available methylaluminoxane [PMAO-S, 9.5 wt% (Al) toluene solution, Tosoh Finechem Co.] were taken to dryness under reduced pressure (at ca. 50 °C for removing toluene, AlMea, and then heated at > 100 °C for 1 h for completion) in the drybox to give white solids. A series of (arylmido)(ketimide)vanadium complexes (3-5, Chart 1) were prepared according to our previous report [7], and were confirmed by ]H, 13C, 51 V NMR spectra. Detailed polymerization procedures were according to our previous reports [4-6]. The resultant polyethylenes were linear confirmed by 'H and I3C NMR, but were hardly soluble in hot o-dichlorobenzene due to the ultra high molecular weight, as reported previously [8], and were impossible to measure GPC to evaluate the molecular weight and the distribution.

18. Effect ofAnionic Ligand in Ethylene Polymerization by (Arylimido)vanadium

125

3. RESULTS AND DISCUSSION 3.1. Synthesis of (arylmido)(ketimide)vanadium complexes (3-5) and ethylene polymerization in the presence of MAO cocatalyst. (Arylimido)(ketimide)vanadium complexes (3-5) shown in Chart 1 were prepared according to our previous report, by treating (ArN)VCl3 with corresponding lithium ketimide in EtjO in high yields (84-85 %) [7], and were identified by 'H, I3C and 51V NMR spectra as well as by elemental analyses. These complexes fold tetrahedral geometry around the vanadium metal center and are 14e species suggested by X-ray crystal structure analyses. Ethylene polymerizations Table 1. Ethylene Polymerization by 1-5 - MAO catalysts. by 3-5 in the presence of complex activity6 Al/Vh ethylene yield MAO were performed in (|imol) /atm /mg toluene, and the results by d 488 1 (1.0) 2500 8 2930 the aryloxide analogues 1-2 under the similar conditions 1 (2.5)d 1000 1770 737 8 d are also cited for comparison. 1000 439 8 1050 2 (2.5) It was revealed that 3-5 1000 8 3(1.0) 384 64 showed high catalytic 3(1.0) 389 2000 65 8 activities and the activities 3(1.0) 111 666 3000 8 were dependent upon the 1000 8 728 121 4(1.0) Al/V molar ratios; the 2000 8 985 164 4(1.0) activities with the molar ratio 4(1.0) 113 6 2000 677 of 3000 seemed the optimum (Table 1). The activities at 2000 368 61 4 4(1.0) 25 °C under the optimized 2500 8 S92 149 4(1.0) conditions increased in the 4(1.0) 128 3000 767 8 order: 1 > 2 > 4 > 3, 5. The 1000 8 661 110 5(1.0) aryloxide analogues 1-2 3000 8 715 120 5(1.0) showed higher the activities than the ketimide analogues "Conditions: toluene 30 mL, 25 °C, 10 min. "Molar ratio. "Activity in kg-PE/mol-V-h. "tited fl»m refs. 5-6. 3-5, and the remarkable difference in the activity between 3 and 5 was not seen. In contrast, 4 showed higher activities than 3, suggesting that the effect of substituent in the ketimide ligand is more dominant than the arylimido ligand for the activity under these conditions. The activities were also dependent upon ethylene pressure, and the activity increased at higher ethylene pressure. The resultant polymers prepared by 3-5 were linear polyethylene confirmed by 'H and 13C NMR spectra, and the attempts for GPC measurement were not successful due to that these polymer samples were hardly soluble even in hot o-dichlorobenzene for GPC analysis, as

126

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seen in the ethylene polymerization by 1 in the presence of various Al cocatalysts and/or in orhanic solvents [6,8], Table 2 summarizes the results for ethylene polymerization performed at various temperatures. As reported previously [5], the catalytic activities by 1-2 decreased upon increasing the polymerization temperature probably due to the decomposition of the catalytically-active species. The optimized temperature by the aryloxide analogues (1, Table 2, Effect of Polymerization Temperature,8 2) were ca. 25 °C, and the temp complex Al/V' yield activity6 activity also decreased at D /mg /C 0 °C. In contrast, the 111 25 3 3000 666 activities by 3 and 5 at 50°C 50 3000 743 124 3 were higher than those at 80 3000 526 88 3 25 °C, but the activities 444 0 2000 74 4 decreased at 80 °C. These 4 25 2000 985 164 results should be a unique 50 4 2000 543 91 contrast that the thermal 80 30 4 2000 178 stability could be improved 25 S 661 110 1000 by using the ketimide 122 50 5 730 1000 analogue in place of the d l 25 1770 737 1000 aryloxide analogues. 834 ld 40 347 1000 Moreover, the activity by 4 60 239 573 ld 1000 at 50 °C was lower than that 2d 25 1050 439 1000 at 25 °C, clearly suggesting 2d 387 40 161 1000 that two ferf-butyl groups "Conditions: 1,2 2.5 ^mol, 3-5 1.0 ^mol, MAO play an important key role to eocatalyst, toluene 30 mL, 10 min. bMolar ratio of Activity in kg-PE/mol-V-h. dCited from ref. 5. improve the thermal stability under the polymerization conditions. 3,2. Effect ofAl cocatalysts for ethylene polymerization by 3-5. We previously reported in the ethylene polymerization using the aryloxide analogues (1,2) that the catalytic activities in the presence of Et2AlCl were much higher than those in the presence of MAO [4,6]. Moreover, we also reported recently [8] that the catalytic activities by the aryloxide analogue 1 were dependent upon both Al eocatalyst and solvent employed [8], Therefore, we explored the effect of Al cocatalysts in ethylene polymerization by the ketimide analogues (3-5), and the results are summarized in Table 3. As reported previously, EtaAlCl was effective as the eocatalyst for ethylene polymerization using the aryloxide analogues (1-2), affording ultra high molecular weight polyethylene with narrow molecular weight distributions [6]. The polymerization also took place in a quasi living manner [6]. However, the

18. Effect ofAnianic Ligand in Ethylene Polymerization by (Arylimido)vanadium

127

observed catalytic Table 3. Effect of Al Cooatalysts and Solvents.* activities by 3-5 in complex ooeatelyst temp. yield activity solvent the presence of /mg /°C EtaAlCl were lower 111 25 3 MAO 666 toluene than those in the 3 42.2 25 253 toluene EfeAlCl presence of MAO. 86.9 521 toluene Et2AlCl 0 3 The activities by 3, 0 105.5 633 »-hexane 3 Et2AlCl 5 in the presence of 25 5 119.5 715 MAO toluene EtjAlCl increased at 53 318 toluene 0 5 Et2AlCl 0 °C, and no 25 105 toluene 17.5 5 EtiAlCl distinct differences 4 767 toluene 127.9 25 MAO in the activities 4 699 toluene 116.5 0 Et2AlCl were observed 4 824 toluene 137.4 25 Et2AlCl when w-hexane was toluene 97 11700 0 Et2A1Cl r used as solvent in toluene 9 1080 0 Et2AlCl place of toluene. In 0 »-hexane 23 2760 EtjAlCl ld contrast, as reported ld 158 19000 C6H5C1 0 Et2AlCl jd previously [8], the 110 13200 0 CH2C12 EtjAlCl observed activities 2C 0 toluene Et2AlCl 115 13700 were highly Conditions: 1,2 0.05 umol, 3-5 1.0 umol, MAO 3.0 mmol arE%AlCl "Activity in kg-PE/mol-V-h. 'Cited dependent upon 250 umol, toluene 30 mL, 10 min. e solvent employed ftom ref. 5. "fated from ref. 8. Polymerization in the co-presence of CCl3CO2Et (10.0 equiv to V). when 1 was used as the catalyst precursor, and the activity in w-hexane was lower than those in other solvent such as toluene, chlorobenzene, dichloromethane under the same conditions. Note that the polymerization by 1 in the co-presence of CClaCOaEt (10.0 eq. to V), which has been known as a mild oxidizing reagent to restart the catalytic cycle from the deactivated state in the polymerization using vanadium(IIT) and/or vanadium(IV) complexes - halogenated aluminum alkyls catalyst systems, showed the significant decrease in the catalytic activity, and the activity decreased upon further addition. The results clearly suggests that the catalytically-active species here were thus apparently different from those prepared from vanadium(III), (IV) complexes. Taking into account these facts, the catalytically-active species should be derived from vanadium(V) containing both arylimido and anionic donor ligand (aryloxide, ketimide) in this catalysis. 4. CONCLUSIONS We have shown that (arylimido)(ketimide)vanadium complexes (3-5) exhibited high catalytic activities for ethylene polymerization, and the activities (by 3 and 5) at 50 °C were higher than those at 25 °C whereas the activities by

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the aryloxide analogues (1,2) decreased significantly upon increasing the polymerization temperature, EtaAlCl was effective cocatalyst for the aryloxide analogues, but the activities by the ketimide analogues were lower than those in the presence of MAO. The role of anionic ancillary donor ligand plays an important key role for exhibiting the remarkable catalytic activity. The facts observed here should be remarkable contrast, and should be important for designing more efficient vanadium complex catalyst for precise olefin coordination polymerization. Acknowledgements This research is partly supported by Tokuyama Science Foundation, and authors express their thanks to Prof. Michiya Fujiki (NAIST) for helpful discussions. J.Y. expresses his thanks to the JSPS for a predoctral fellowship (No. 5042), and K.N. expresses his thanks to Tosoh Finechem Co. for donation of MAO. References [1] G. J. P. Britovsek, V. C. Gibson, and D. F. Wass, Angew. Chem., Int. Ed. Engl.38(1999)429. [2] V. C. Gibson and S. K. Spitzmesser, Chem. Rev. 103 (2003) 283, [3] For reviewing article, K. Nomura, in: L. P. Bevy (Ed.), New Developments in Catalysis Research, Nova Science Publishers, New York, 2005, p. 199. References are cited therein.

[4] K. Nomura, A. Sagara, and Y. Imanishi, Macromolecules 35 (2002) 1583. [5] W. Wang, J. Yamada, M. Fujiki, and K. Nomura, Catal. Commun. 4 (2003) 159. [6] W. Wang and K. Nomura, Macromolecules 38 (2005) 5905. [7] J- Yamada, M. Fujiki, and K. Nomura, Organometallics 24 (2005) 2248. [8] W. Wang and K. Nomura, submitted for publication.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

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19 Computational Approach on the Interaction between CrO 3 and Ethylene as a Model for the Understanding of Phillips Catalyst Boping Liu*, Wei Xia, Minoru Terano School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Ishikawa 923-1292, Japan, Email: [email protected]

Abstract Supporting of bulky CrO3 onto SiO2 surface is crucial for achieving activity for industrial Phillips CrOx/SiO2 catalyst. However, mechanistic understanding of the supporting effect has not been achieved yet. In this work, the molecular orbital interaction between CrOa and ethylene was investigated using DFT and PIO methods. It was demonstrated that bulky CrOj without supporting onto SiO2 surface is difficult to achieve activity for ethylene polymerization like Phillips catalyst because formation of stable it-bonded molecular complex between CrO3 and ethylene monomer could block the whole activation process. Keywords: Phillips catalyst; Chromium trioxide; Ethylene; Density functional theory (DFT); Paired interacting orbitals (PIO) 1. INTRODUCTION As one of the most important industrial olefin polymerization catalysts, Phillips CrOx/SiO2 catalyst is still producing about 7 million tons of high density polyethylene (HDPE) per year in the world. Its HDPE product usually shows ideal processability especially for blow molding [1]. It is most interesting that this catalyst shows high polymerization activity without using any activator like Al-alkyl although it can also be activated by Al-alkyl [2] or CO [3]. Ethylene can act as an activator to reduce and alkylate the chromium species followed by initiation of ethylene polymerization [4, 5], In fact, the specific mechanisms concerning the activation including reduction and alkylation of surface

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B.LiuetaL

chromate species (Cr(VI)Ox, surf) are still remained mysterious even after SO years of great research efforts [1,6]. Phillips catalyst for ethylene polymerization can be synthesized through simple but most important thermal activation (or calcination) process using CrO3 and amorphous SiO2 as raw materials [1]. During the calcination process at high temperature (usually around 600~800°C), the bulky CrO3 must be supported onto SiO2 surface as chromate species [7, 8], Otherwise, no polymerization activity can be achieved from unsupported bulky CrO3. Up to now, the supporting effect for CrO3 not been well has understood. Once C1O3 was supported as chromate species on pj SiO2 surface, the chromate species (Cr(VI)Ox, Burf) can be Scheme 1 Proposed reaction mechanisms of the reduction 1 »ri J t. *. 1 „, of hexavalent CrGompoundB by ethylene monomer

_ . „ . - . r<-^n\r\ reduced into Cr(Il)Ox, v

J

surf

by ethylene monomer with simultaneous formation of two formaldehyde molecules (reaction (1) shown in Scheme 1) [4, 5]. Cr(II)OXj surf species is the final precursor of active site for ethylene polymerization. Our recent theoretical investigation on this reaction using density functional theory (DFT) and paired interacting orbitals (PIO) showed that the preferential intermolecular orientation for the reaction between ethylene monomer and monochromate species shown in reaction (1) of Scheme 1 was elucidated in terms of low repulsive interaction and in-phase overlap of molecular orbital interaction in-between the intermolecular frontier region [9]. In this work, molecular orbital interactions under various intermolecular geometric orientations between ethylene monomer and bulky CrO3 will be studied through a theoretical approach in combination of DFT and PIO methods. The results have demonstrated that a similar reduction of CrO3 by ethylene into CrO and formaldehyde (reaction (2) in Scheme 1) seems not plausible indicating the importance of supporting bulky CrO3 onto SiO2 to achieve ethylene polymerization activity for Phillips CrfVSiOa catalyst. 2. COMPUTATIONAL METHODS Details concerning the basic theoretical and mathematic bases of PIO method can be found in the literature and will not be introduced again herein [9-12]. Equilibrium structure of &O3 in ground state were calculated by DFT method (B3LYP, basis set: 6-31G*) using SPARTAN*02 Windows developed by

19. Computational approach on the interaction between CrOj and ethylene

131

Wavefunction, Inc. Surface electron density, surface potential and electrostatic charges of each atom were obtained. Data for ethylene were directly used from our previous report [9]. These optimized molecular structures were used for the subsequent PIO calculations, LUMMOX software for Windows PC computer was used for calculation of intermolecular orbital interaction by PIO method. As shown in Fig. 1, six typical intermolecular orientations namely GO-1, GO-2, GO-3, GO-4, GO-5 and GO-6 between CrO3 and ethylene with an intermolecular distance of 3A (distance between Cr atom and C=C bond) were calculated by PIO method. The interacting molecular system between CrO3 and ethylene was defined as combined system C, in which CrO3 and ethylene were named as fragment A and fragment B, respectively. The extended Hiickel calculations were used to obtain the canonical molecular orbitals. The interaction between A and B in C could be well represented by 12 pairs of localized orbitals. In each orbital pair, one orbital belongs to fragment A and the other orbital to fragment B.

Y Y (a)

(b)

(c)

(d)

(e)

(t)

Figure 1 Six typical molecular orientations between CrO3 and ethylene considered for the calculation of molecular orbital interaction by PIO method in this work, (a) GO-1; (b) GO-2; (o) GO-3; (d) GO-4; (e) GO-5; (f) GO-6. The elements are coded in an increasing gray scale sequence as follows: H (white) < C < O < Cr (Black)

3. RESULTS AND DISCUSSION

(a)

(b)

Figure 2 Electron density, molecular orbitals of HOMO and LUMO of C1O3 computed by DFT method, (a) electron density; (b) HOMO; (c) LUMO (Side view), (d) LUMO (Top view), Computation conditions: DFT method B3LYP, basis set: 6-31G*

Optimized equilibrium geometry structure of CrO3 showed a bond length of Cr=O 1.576 A and a bond angle O=Cr=O 120°. Electron density, molecular orbitals of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) of CrO3 computed by DFT method are shown in Fig, 2. Dipolar property of CrO3 shows a value of 0 debye due to its planar and symmetric structure. HOMO of CrO3 mostly comprised of atomic

B. Liu et al.

132

orbitals from oxygen atoms. LUMO comprised of a large contribution from atomic orbitals of Cr atom and a small fraction from oxygen atoms. Energy of HOMO and LUMO is - 9.06 eV and - 5.62 eV, respectively, with a band gap of 3.44 eV. Electrostatic potential results showed the atomic charges for all atoms are Cr: + 1.320, O: - 0.440 with a total charge of 0. Table 1 Htfckel energies of the interacting systems under the six typical molecular orientations between CrOa and ethylene calculated by PIO method Molecular orientations *

E c (eV) b )

AE c (eV) c )

Overlap population for PIO-1

GO-1

- 616.49

+ 0.61

- 0.076

GO-2

- 686.05

+ 1.05

-0.145

GO-3

- 687.38

-0.28

+ 0.109

GO-4

- 6§7.38

-0.28

+ 0.109

GO-5

- 682.54

+ 4.55

- 0.387

GO-6

- 682.96

+ 4.14

- 0.054

a) Intermolecular distance between Cr atom and C=C bond is 3A for all six orientations. b) C: interacting system between A and B, E c : Hiiekel energy of interacting system C at an intermolecular distance 3A between A and B c) AEC = E c - EDG EQC= E°A + E°B, E° c : Hiickel energy of a summary of A and B, E"A (A: CrO3) = - 472.71 eV, E°B (B: ethylene) = - 214.39 eV, E° c = - 6S7.10 eV

Hiickel energies of the combined interacting systems C (E c ) at an intermolecular distance of 3A (distance between Cr atom and C=C bond) between A (CrOs) and B(ethylene) for the six typical intermolecular orientations namely GO-1, GO-2, GO-3, GO-4, GO-5 and GO-6, as well as the Huckel energies for isolated A (E°A) and isolated B(E°B), energy increase (AEc= Ec - E°c, in which E°c= E°A + E°B) before and after interaction were shown in Tab. 1. As it can be seen from Tab. 1, the combined interacting system C shows energy decrease only at GO-3 and GO-4 compared with those at other four intermolecular orientations indicative of attractive interaction between A and B. These results are consistent with the DFT calculation results regarding the electrostatic charge distribution in CrO3. Coulombic attractive interaction between the positively charged Cr and the two negatively charged carbon atoms in ethylene should be the governing factor to direct the ethylene molecule in approaching to CrO3 at GO-3 and GO-4. Extended Huckel calculations were used to obtain the canonical molecular orbitals for the combined interacting system C at GO-3. 12 pairs of localized orbitals were obtained. In each orbital pair, one orbital belongs to fragment A and the other orbital to fragment B. The eigenvalues on pairwise transformation indicate that PIO-1 within the 12 pairs made 94.1 %of contribution in the

19, Computational approach on the Interaction between CrO$ and ethylene

.

—

-

133

.

-

(c) Figure 3 Contour maps of PIO orbitals of the interacting system C at molecular orientation GO-3 and GO-4, (a) GO-3, PIO-l(l), (b) GO-3, PIO-1(2) the cross section perpendicular to that in (a) through Cr atom; (c) GO-4, PIO-1 (1), (d) GO-4, PIO-1 (2) the cross section perpendicular to that in (c) through Cr atom

intermolecular orbital interaction at GO-3. Analysis of the other 11 pairs of PIO orbitals (from PIO-2 to PIO-12) could be neglected due to their too low contribution in the interaction. Contour maps of PIO-1 of the interacting system C at the intermolecular orientation GO-3 are shown in Fig, 3 ((a) and (b)). P1O1 shows in-phase molecular orbital interaction at GO-3, which is consistent with their positive overlap populations (Tab. 1). PIO calculation results for the expression of PIO-1 in terms of a linear combination of atomic orbitals (LCAO) are shown in Eqs. (1) and (2) as follows. = - 0 . 7 9 1 C r 3 ^ 2 ^ - 0 . 4 6 3 C r 3 * 2 + 0.358Cr4S ( ) = -0.624C(l) 2 ^-0.624C(2) 2 i > PIO-1 (A) = 0.983 LUMOA PIO-1(B) = - 0.996 H0M0 B

(1) (2) (3) (4)

Minor contributions from various atomic orbitals were omitted in these equations, from which the main components (Cr 3Dx ~y , Cr 3 D g 2 , Cr 4S and C 2Py) of atomic orbitals can be observed to form the attractive interaction between A and B at GO-3. PIO-1 orbital could also be expressed in terms of a linear combination of molecular orbitals (LCMO) calculated from molecular A and B, respectively, as shown in Eqs. (3) and (4). In Eqs.(3) and (4), those minor contributions from various molecular orbitals were omitted. The main components of molecular orbitals for PIO-1 orbitals of GO-3 for the formation of the attractive interaction between A and B at GO-3 can be observed to be LUMOA and H0M0 B . It is noticeable to see that the intermolecular orbital interaction at GO-3 is mostly derived from LUMO and HOMO of CrOa and ethylene, respectively.

134

B.Lmetal

Extended Hiickel calculations were also used to obtain the canonical molecular orbitals for the combined interacting system C at GO-4. Similar LCAO and LCMO results were obtained. Only the contour maps of PIO-1 of the interacting system C at the intermolecular orientation GO-4 are shown in Fig. 3 ((c) and (d)). It was further confirmed that PIO-1 orbitals at GO-1, GO-2, GO-5 and GO-6 all show repulsive intermolecular interaction between A and B. Calculation results here demonstrated that a similar reduction of GO} by ethylene into CrO and formaldehyde (reaction (2) in Scheme 1), which requires an intermolecular orientation of GO-2, seems not plausible indicating the importance of supporting bulky CrO3 onto SiO2 for ethylene polymerization activity. Moreover, the formation of stable Jt-bonded molecular complex between CrO3 and ethylene can be expected. 4. CONCLUSIONS Interaction between CrO3 and ethylene was investigated in a molecular orbital level using DFT and PIO methods as a model for the mechanistic understanding of Phillips CrOx/SiO2 catalyst. It was demonstrated that bulky CrO3 without supporting onto S1O2 surface is difficult to achieve activity for ethylene polymerization because formation of stable ji-bonded molecular complex between CrO3 and ethylene monomer could block the whole activation process. References [I] M. McDaniel, Adv. Catal. 33 (1985) 47-98. [2] B. Liu, P. Sindelaf, Y. Fang, K. Hasebe, M. Terano, J. Mol. Catal. A: Chem. 238 (2005)142-150. [3] Y. Fang, B. Liu, K. Hasebe, M. Terano, J. Polym. Sci. Part A: Polym. Chem. 43(2005)4632-4641. [4]B. Liu, H. Nakatani, M. Terano, J. Mol. Catal. A: Chem. 184 (2002) 387398. [5]B. Liu, H. Nakatani, M. Terano, J. Mol. Catal. A: Chem. 201 (2003) 189197. [6] E. Groppo, C. Lamberti, S. Bordiga, G. Spoto, A. Zeechina, Chem. Rev. 105 (2005)115-183. [7] B. Liu, Y. Fang, M. Terano, J. Mol, Catal. A: Chem, 219 (2004) 165-173. [8] Y. Fang, B. Liu, M. Terano, Appl. Catal. A: Gen. 279 (2005) 131-138. [9] B. Liu, Y. Fang, M. Terano, Mol. Simula! 30 (2004) 963-971. [10] B. Liu, Y. Fang, W. Xia, M. Terano, Kinet. Catal. 47 (2006) 234-240. [II] A. Shiga, H. Kawamura, T. Sasaki, J. Mol. Catal. A: Chem. 77 (1992) 135152, [12] H. Fujimoto, Ace. Chem. Res. 20 (1987) 448-453.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

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20

Olefin Polymerization by Bimetallic Zr Catalyst. Ligand Effect for Activity and Stereoselectivity Junpei Kuwabara, Daisuke Takeuehi, and Kohtaro Osakada* Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Yokohama, 226-8503, Japan

Abstract Bimetallic Zr complexes are synthesized by olefin metathesis reaction of vinyl group of monometallic complexes. The Si bridged zirconocene {rfC5Me4-SiMe2-ri5-C5H3CH2CH=CH2}ZrCl2 is transformed by metathesis reaction to the novel bimetallic complex with arasa-strueture. Ethylene and propylene polymerization was conducted by bimetallic complexes. The activity of the bimetallic complex depends on the steric hindrance of the ligand. The bimetallic complex with aasa-structure gave isotactic polypropylene with a similar high selectivity to that of the monometallic analog. Bimetallic complexes catalyzed cyclopolymerization of 1,5-hexadiene to give poly(methylene-l ,3-cyclopentane). 1. INTRODUCTION Group 4 metallocene catalysts have been widely investigated for olefin polymerization]!]. Recent progress of metallocene catalyst is led to stereospecific polymerization of a-olefm[2]. Design of new catalysts with bimetallic structure would exhibit a unique performance originated from cooperative effect of the two metal centers. During the last decade, several groups reported preparation of the bimetallic complexes of Ti and Zr, and their olefin polymerization[3]. Since the catalytic behavior strongly depends on bridging ligand, we have investigated the relationship between catalytic activity and structure of bridging chain[4]. Herein, we report the effect of ligand structure around metal center of bimetallic Zr complexes for ethylene and

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J. Kuwabara et al

propylene polymerization. Since nietallocene catalyst promotes polymerization of non-conjugated diene such as 1,5-hexadiene as well as olefln polymerization[5], cyclopolymerization of 1,5-hexadiene by bimetallic catalyst were also investigated. 2. EXPERIMENTAL Materials. All the manipulations of the air-unstable complexes were carried out under nitrogen or argon using standard Schlenk techniques. Toluene, hexane, and EtaO were distilled from sodium benzophenone ketyl and stored under nitrogen or argon. MAO was purchased from TOSOH-FiNECHEM and stored under nitrogen or argon. 1, 2,3, 4 and 5 were prepared according to the method reported previously[4]. 6 was prepared in similar manner to the previous report[4]. 'H NMR (300 MHz, C6D6): 6 (major) : 8 6.75 (t, 2H, J=2 Hz, cyclopentadienyl), 5.79 (m, 2H, olefmic), 5.39 (t, 2H, J=3 Hz, eyclopentadienyl), 5.13 (t, 2H, J=3 Hz, cyclopentadienyl), 3.5-3.7 (m, 4H, CH2), 2.03, 2.00, 1.76, 1.66 (s, 24H, C5Me4), 0.39, 0.38 (s, 12H, SiMea). 6 (minor): 5 6.80 (t, 2H, J=2 Hz, cyclopentadienyl), 5.83 (m, 2H, olefinic), 5.41 (t, 2H, J=3 Hz, cyclopentadienyl), 5.16 (t, 2H, J=3 Hz, cyclopentadienyl), 3.5-3.7 (m, 4H, CH2), 2.03,2.00,1.76, 1.65 (s, 24H, C5Me4), 0.39, 0.37 (s, 12H, SiMe2). Polymerization Procedure. Typical experimental procedure for ethylene polymerization is as follows. To a solution of 1 (4.3 mg, 0.01 mmol) in toluene (6.4 niL) was added a toluene solution of MAO (2.79 M-Al, 3.6 mL, 10 mmolAl). The catalyst solution (1.0 mM-Zr) was stirred at room temperature for 15 min for the pre-activation. To a toluene (30 mL) saturated with ethylene (1 atm) was added the solution of the catalyst (0.50 mL, 0.50 pmol). The solution was stirred for 5 min under atmospheric ethylene at 15 °C. The reaction was quenched with MeOH and 5 M HCl-MeOH. Separated polyethylene solid was filtrated, washed with MeOH, H2O, and hexane, and dried in vacuo. In the case of Zr bimetallic catalyst, 0.25 (jmol catalyst was used. Analytical Procedure. Gel permeation chromatography (GPC) was performed on a TOSOH HPLC-8121GPC/HT using orthodichlorobenzene (152 °C) as eluent for polypropylene and on Waters 150CV using orthodichlorobenzene (135 °C) as eluent for poly(methylene-l,3-cyclopentane). NMR spectra ('H and 13 C{'H}) were recorded on JEOL JNM LA-500 or Varian Mercury 300 spectrometers. Sample solutions of polyethylene were prepared in 1,1,2,2tetrachloroethane-rf2 and the central peak of the solvent (74.0 ppm) was used as an internal reference. Sample solutions of polypropylene and poly(methylene1,3-cyclopentane) were prepared in CDCI3 and the central peak of the solvent (77.0 ppm) was used as an internal reference.

20, Olefin Polymerization by Bimetallic Zr Complex

137

3. RESULTS AND DISCUSSION 3,1. Synthesis of bimetallic complexes Ru catalyst promotes olefin metathesis reaction of vinyl group of 1-3 to give bimetallic Zr complexes 4-6, respectively, according to the previous report[4]. The coupling reaction of 3 gives bimetallic complex 6 as a mixture of meso and racemic diastereomers because of the planar chirality on the cyclopentadienyl complex. ] H NMR spectrum of the reaction mixture shows 3:4 molar ratios of the isomers. Recrystallization changed the ratio to 9:1 due to a difference of solubility between the isomers. "iSi. , Zr^

•ci

*

4

5

«C1

01/,,.

6

3,2. Olefin polymerization by bimetallic Zr complexes. The monometallic and bimetallic complexes catalyze polymerization of ethylene in the presence of MAO ([Zr] = 16.7 uM and [Al]/[Zr] = 1000 in toluene). Activities of the catalysts are estimated from the polymer yield of the reaction for a short period (5 min) at 15 °C in order to avoid the mass transfer effect[6]. Bimetallic complex 4 exhibits higher catalytic activity (3020 g mmol"'h"') than that of mononuclear precursor 1 (2350 g mmor'h"1). On the other hand, S has a slightly lower activity 4000 (3600 g mmor'h"') than that of 2 (3730 g mmol"'h"'). The catalytic activity of 6 (426 g -_ 3000 mmol"'h"') is significantly lower than that of 3 o (1420 g mmor'h 4 ). We proposed that E enhancement of dissociation of the active Zr 3 2000 cation and the MAO-derived anion due to the 1000 bimetallic structure resulted in higher activity of 4 than 1[4]. Low activity of S can be Monometallic Bimetallic attributed to steric hindrance of fluorenyl catalyst catalyst group. Since two metallocene groups are close to each other, fluorenyl ligand on a Figure 1. Ethylene polymerization metal center probably retards smooth activity of Zr complexes.

138

J, Kuwabara et al

polymerization on the other metal center. The effect of steric hindrance in 6 is larger than that of fluorenyl group in 5 because methyl groups on eyclopentadienyl ligand are orientated to the Zr center. These results indicate that the position of substituent on the ligand affects the activity of bimetallic complex. Low catalytic activity has been reported for the bimetallic complex having bulky ligand such as CsHMe4[7]. In propylene polymerization, 6 has low catalytic activity than that of 3, which is similar to the ethylene polymerization (Table 1). Si-bridged catalyst 3 has an allyl group at ^position. This C\ symmetric catalyst produced isotactic polypropylene (mmmm=88%) via back-skip mechanism as reported by Marks et a/[8]. 6 also gives highly isotactie polypropylene (mmmm=86%). The isotacticity was independent of monomer pressure. The isospecific bimetallic catalyst is rare example [9]. The metathesis method constructs bimetallic structure without loss of catalytic property of monometallic precursor. Table 1 Propylene polymerization3. m pentad Propylene Cat. Activity Entry (atm) (g mmorV1) (%) 1 29 88 1 3 2.5 2 86 3 181 1 18 86 6 3 87 86 6 2.5 4 a [Zr] = 187 JIM, [AI]/[Zr] = 1000, 1 h, 30 m L toluene, r.t.

Mn 2600 5000 2600 4800

1.5 2.2 2.1 2.0

3.3. Cyclopolymerization ofl,5-hexadiene by bimetallic Zr complexes. Zr complexes in combination with MAO catalyze polymerization of 1,5hexadiene to give poly(methylene-l,3-cyclopentane) (PMCP). Table 2 shows results of polymerization by various Zr complexes. These polymers contain negligible amount of acylic unit, which are confirmed by 13C{'H} NMR. spectra. Bimetallic complexes 4-6 gave high molecular weight polymer in comparison with monometallic 1-3. Especially, molecular weight of the polymer formed by 5 is approximately two times larger than that by 2. Figure 2 shows 13C{'H} NMR spectra of aliphatic region and expansion of the spectra from 31 ppm to 34 ppm. The spectrum of the polymer obtained by 4 indicates trans-rich structure based on the strong signals around 33.3 ppm (Figure 2a). Figure 2b shows signals of methyl end group at 21.3 ppm (trans) and 21.1 ppm (cis) as well as signals of cyclic structure of main chain. The spectrum of the polymer formed by 4 shows =CH2 signals of the terminal group at 153.2 and 104.6 ppm instead of that of methyl end group. Thus, the polymer formed by 4 has methylenecyclopentyl end groups. On the other hand, 5 affords the polymer with both methylcyclopentyl and methylenecyclopentyl end group. The content

20. Olefin Polymerization by Bimetallic Zr Complex

139

of methyl end group increases with the increase of the steric hindrance of the ligand around metal center. Waymouth et al reported cyclopolymerization of 1,5-hexadiene by (CsMe5)2ZrCl2 to give methyl terminated polymer[10]. Catalyst with bulky ligand undergoes chain transfer of the growing chain from Zr center to Al compounds in preference to pl-H elimination as termination of propagation. Signals of 4 and 5 positions of cyclopentane ring provide information for tacticity of the polymer[5]. The spectrum shows signals at 31.78, 31.82 and 31.96 ppm for cis rings and signals at 32.28, 34.32 and 34.39 ppm for trans ring (Figure 2c). These results indicate that 4 gave ataetie PMCP. On the other hand, Figure 2d has very small signals at 31.86 and 34.32 ppm, suggesting that 6 affords isospecific PMCP. Both the bimetallic and monometallic complexes show similar trans-selectivity and tacticity in the polymerization. Me

4

5

4

5 /M

(a)

4,5 trans

1,3 t

4,5 t

4,5 cis

1,3 c 4,5 c

2c 2t _JA.

^

.P, il

(d)

Me end group tc I

45

40

35

30

25

20

34

{

J \ 33

32

31

Figure 2. 13C{'H} NMR spectra of PMCP produced by (a) 4 and (b)6. The extended the spectra of PMCP by (c) 4 and (d) 6. Table 2 Polymerization of 1,5-hexadienea. Entry Yield Mn Cat. MwtMn

a

trans:cis

Tacticity

77:23 1 12800 1.7 1 41 Ataetic 2 2 21 45:55 Atactic 12000 1.6 59:41 3.6 10300 40 3 3 Isotactic 4 4 44 1.7 78:22 Ataetic 13700 S 3.2 5 31 44:56 Atactic 22700 1.9 6 35 58:42 Isotactic 13200 e [Zr] = 200 yM, [monomer]/[cat.] = 2000, [AI]/[Zr] = 1000, 3 h , 25 mL toluene, r.t.

140

J, Kmvahara et al

4. CONCLUSIONS The catalytic activity of bimetallic Zr catalyst strongly depends on the steric hindrance of the ligand. The bimetallic complex with oara-structure undergoes isospecific propylene polymerization, which is similar to monometallic analog. This result indicates that the metathesis coupling reaction constructs bimetallic structure without loss of catalytic property of monometallic precursor. The ansa-type bimetallic catalysts also catalyze isospecific polymerization of 1,5hexadiene. Acknowledgements This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science, Sports, and Culture, Japan and by the 21st Century COE program. J. K. acknowledges JSPS Research Fellowship for Young Scientist. The authors thank Prof, Takeshi Shiono, Dr. Kei Nishii and Mr. Mitsuhiro Okada for GPC measurement. References [1] H. H, Brintzinger, D. Fischer, R, Mulhaupt, B. Rieger, R. M. Waymouth, Angew. Chem., Int. Ed. Engl. 34 (1995), 1143-1170. [2] L. Resconi, L. Cavallo, A. Fait, F. Piemontesi, Chem. Rev. 100 (2000) 1253-1345. [3] (a) S. Jttagling, R. Mulhaupt, J. Organomet. Chem. 460 (1993) 191-195. (b) S. K. Noh, J. Kim, J. Jung, C. S. Ra, D. Lee, H. B. Lee, S. W. Lee, W. S. Huh, J. Organomet. Chem. 580 (1999) 90-97. (c) L. Li, M. V. Metz, H. Li, M. Chen, T. J. Marks, L. Liable-Sands, A. L. Rheingold, J. Am. Chem. Soc. 124 (2002) 12725-12741, and references therein. [4] J. Kuwabara, D. Takeuchi, K. Osakada, Organometallics 24 (2005) 27052712. [5] (a) L. Resconi, R. M. Waymouth, J. Am. Chem. Soc. 112 (1990) 4953-4954. (b) G. W. Coates, R. M. Waymouth, J. Am. Chem. Soc. 115 (1993) 91-98. [6] Y.-X. Chen, M. V. Metz, L, Li, C, L, Stern, T. J, Marks, J. Am, Chem. Soc. 120(1998)6287-6305. [7] G. Tian, B. Wang, S. Xu, X. Zhou, B. Liang, L. Zhao, F. Zou, Y. Li, Macromol. Chem. Phys. 203 (2002) 31-36. [8] M. A. Giardello, M. S. Eisen., C. L. Stern, T. J. Marks, J. Am. Chem. Soc. 117(1995)12114-12129. [9] W. Spaleck, F. Kiiber, B. Bachmann, C. Fritze, A. Winter, J. Mol. Catal. A: Chem. 128 (1998)279-287. [10] A. Mogstad, R. M. Waymouth Macromolecules 25 (1992) 2282-2284.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

141

21 Synthesis, Characterization and Ethylene Reactivity of 2-Ester~6-iminopyridyl Metal Complexes Wenjuan Zhang, Biao Wu, Wen-Hua Sun* Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China

Abstract A series of late-transition metal complexes such as iron (L)FeCl2 (3a-f), cobalt (L)CoCl2 (4a-f), nickel (5a-f) and palladium(6a-f) complexes have been prepared by the reaction of 2-carboxylate-6-iminopyridine 2a-f [2-COOEt-6(2,6-R2CfiH3N=CCH3)CsH3N (2a: R = CH3, 2b; R = Et, 2c: R = i-Pr, 2d: R = F, 2e: R = Cl, 2f: R = Br)] with MC12 (M = Fe, Co, Ni or Pd). These complexes were characterized by elemental analysis, IR spectroscopy and X-ray crystallography. These complexes were tested for ethylene oligomerization and polymerization in the presence of MAO under various reaction conditions. The iron complexes exhibited high catalytic activities for ethylene polymerization/ oligomerization, whereas the cobalt complexes showed moderate activities for the polymerization and high activities for the oligomerization. In addition, the iron catalysts predominantly produced linear oligomers and polyethylene with vinyl group. Nickel complexes showed remarkably high catalytic activities for the ethylene oligomerization affording C4-C8 olefins as the main products, although the selectivity of a-olefm was very low. Palladium complexes showed moderate activity for the ethylene oligomerization and polymerization, and the oligomer product was only C4. These facts indicated that the nature of the metal core strongly affects toward the catalyst behavior in these catalyses.

142

W. Zhang etal

1. INTRODUCTION Olefin polymerization catalyzed by late transition metal complexes has received great prominence over the past decade especially since Brookhart's report on Pd (II) and nickel(II) diimine catalyst systems which showed notable catalytic activity for both ethylene and a-olefin polymerization [1]. Following this pioneering work, various modified bidentate nitrogen ligands, such as bipyridine ligands, imino-pyridine compounds were reported [2]. During the course of synthesis of diaeerylpyridine, we established the synthetic procedure for 2-ethylcarboxylate-6-acetylpyridyl. We thus prepared various late transition metal complexes containing a series of ligands of this type and tested these complexes for ethylene oligomerization/polymerization [3]. In this paper, we present that nature of the centered metal directly affected the catalytic behavior, 2. EXPERIMENTAL Ethyl 6-acetylpyridine~2-carboxylate was initially synthesized by the reaction of 2,6-dicarbethoxypyridine with ethyl acetate in the presence of CaH5ONa using the modified procedure for the synthesis of 2,6-diaeetylpyridine [3b]. The optimal molar ratio of QjHsONa to 2,6-dicarbethoxypyridine was determined to be 1.1-1.5 in order to obtain compound 1 in an acceptable yield, whereas 2,6-diacetylpyridine was produced with the molar ratio (4.5:1) of CaHjONa to 2, 6-diearbethoxypyridme. The pyridylimine ligands 2a-c were easily prepared in satisfactory yields (68.2-73.0 %) through the Schiff-base condensation of 1 with anilines in the presence of catalytic amount of ptoluenesulfonic acid (p-TsOH) under refluxing toluene [3b]. The complexes were obtained by treating ligands with corresponding MCI2CM = Fe, Co, Ni, Pd). 3. RESULTS AND DISCUSSION J. 1. Syntheses and characterization of complexes. Scheme 1 shows synthesis of the ligands and complexes. Comparing the IR spectra of the ligands with corresponding complexes, the C=N stretching frequencies were shifted due to the coordination interaction between the imino nitrogen atom and the metal center. Most structures of these complexes were confirmed by X-ray crystallography, and Figure 1 shows the selected examples. The structure indicated that the different geometry of coordination was strongly dependent upon the centered metal employed. For the iron and cobalt complexes, the coordination geometry was similar, and two nitrogen atoms coordinated metal cores. The nickel atom was coordinated by two nitrogen

21. Synthesis and Ethylene Reactivity of2-Ester-6-iminopyridyl Metal Complexes

143

atoms and one oxygen atom. The structure by palladium possessed square planar around the metal center coordinated by two nitrogen atoms

HOOC

N

"COOH

EtOH reflux

CH3COOEt EtOOC

N

COOEt 1-1 equivof EtONa 2a: R = Me; 2b: R = Et; 2c: R = i-Pr; 2d: R = F; 2e: R = Ci; 2f: R = Br.

EtOOC

EtO. Fe Co Ni Pel

Me

Et

i-Pr

F

CI

Br

3a 4a Sa 6a

3b 4b

3c 4c 5c 6c

3d 4d 5d 6d

3e 4e 5e 6e

3f 4f 5f 6f

Sb 6b

Scheme 1, Reagents and conditions: i) toluene, p-TsOH, ii) toluene, /?-TsOH, silica-alumina catalyst support, 4 A molecular sieves, iii) FeClj, CoCl2 and NiClz in ethanol; PdCl2 in CH2C12.

Figure 1. Structure of MC12(L) (M= Fe, Co, Ni, Pd)

3.2. Ethylene oligomerization and polymerization in the presence of MAO. These complexes were investigated in detail as the catalyst precursor for ethylene oligomerization/polymerization (ethylene 1 or 10 atm). In general, complexes 3a-f showed considerable activity for ethylene oligomerization to produce butenes and hexenes (with a little of high oligomers) at 1 atm ethylene

144

W. Zhang et al

pressure. Simultaneously, the catalyst systems of 3a and 3b produced some polyethylene. However, complexes 3d-f showed higher activity for oligomerization than 3a-3b, which indicated that the ligand environment significantly affected the catalytic activity. The cobalt complexes 4c, 4f showed higher activity for oligomerization. The nickel complexes 5c, 5f showed notable activity for ethylene oligomerization and polymerization. However, the palladium analogues were inactive at 1 atm. The effect of auxiliary ligand toward the catalyst activity was also investigated. However, as shown in Table 1, only a slight increase in activity was observed relative to the catalytic system of 3i/MAO (entries 6, 7 in Table 1). The results show that addition of PPhato the reaction led to the increase of the oligomerization activity of 4f/MAO. For nickel complexes, the ethylene oligomerization activities of 5c, 5f were significantly improved in the presence of PPh3as auxiliary ligands (entries 11,12,13,14 in Table 1). Table 1 Ethylene oligomerization and polymerization with 3 a - 6 f / MAO at 1 atm a Entry

Complex

Al/Fe

Temp

(mol)

C°c)

Oligom distribution11(%) C4/ZC

Activity

Cfi/IC

Linear

lff^g-mol-Mf'-h"1 aHgora13

Polym

3.35

aolefin >99

2.17

9.44

1

3a

1OOO

15

92.40

4.25

2

3b

1000

15

71.15

28.84

-

97.1

1.61

0.91

>99

3

3c

1000

15

98.20

1.50

0.3

1.39

trace

4

3d

1000

15

84.04

0.90

15.06

94.6

2.60

no

5

3e

1000

15

35,42

57.74

6.84

97.7

6.04

trace

S

3f

1000

15

77.96

2.89

19.15

93.3

1.80

trace

7C

3f

1000

15

100

-

-

>99

2.45

no

8

4c

1000

15

55.34

27.17

17.49

98.1

5.32

3.50

9

4f

1000

15

72.11

23.78

4.10

95.6

18.90

trace

10e

4f

1000

15

71.28

23.28

5.23

92.2

31.70

no

11

Sc

1000

15

48.53

8.73

42.74

7.9

5.47

1.37

C

12

Sc

1000

15

76.49

21.62

8.8

65.2

no

13

Sf

1000

15

70.15

21.89

51.0

9.04

0.30

14C

Sf

1000

15

81.68

17.09

8.7

79.2

no

7.96

"General conditions: 5 nmol precatalyst; 30 m L toluene; reaction time 30 m i n ^ D e t e r m i n e d by GC, £ C means the total amounts of oligomers. C2 equiv of PPhj as auxiliary ligand

21, Synthesis andEthylene Reactivity of2-Ester-6-iminopyridyl Metal Complexes

145

The complexes were also investigated for ethylene polymerization at 10 atm ethylene pressure. The results were listed in Table 2, Comparing the data in Table 2 with that in Table 1, the iron complexes containing less bulky-substituted ligand were found to show the higher catalytic activity. The distribution of olefin oligomers follows the Schulz-Flory rules, which are characterized by the constant K that represents the probability of chain propagation. As shown in Table 2, increasing the steric bulk at the orthoposition of the aryl group on the iron complexes led to an increase in K value (entries 1, 2 and 3 in Table 2). GC and GC-MS analysis of the oligomers indicated that the selectivity for linear a-olefms was higher than 78% for 3a-f at 10 atm of ethylene. Moreover, DSC studies determined the Tm values are in the range of 88 to 132 °C, which are well correlative with the linear characteristics of the PE samples with low molecular weight. For cobalt complexes, the ethylene pressure had little effect toward the activity. Dimers and trimers are major products (with a little amount of higher carbon number oleflns) and the linear a-olefins are the predominant products. The activity by nickel complexes increased upon increasing the ethylene pressure, and 4c and 4f generate butenes and hexenes as main oligomeric product and the distribution of oligomers did Table 2 Ethylene oligomerization and polymerization with 3a—fiMAO at 10 atmB Entry

Complex (umol)

Polym (g)

Mnc

Activity 1

10 g'mol-Mt-'-lf

PDF

3

(10 )

Oligom

Polym

6.20

56.70

4.7

32.7

m d lm

linear

(°C)

a-olefin (%)

132

88.8

0.83

K

1

3a (42.3)

24.00

2

3b (53.9)

1.15

1.44

2.10

1.3

90.3

122

82.1

0.93

3

3c (36.5)

1.13

1.90

3.20

1.0

4.2

124

92.1

0.96

4

3d (34.1)

trace

4.06

-

-

-

-

78.3

0.73

E

5

3e (42.5)

1.67

30.60

3.90

0.5

2.4

88

92.0

0.81

6

3f(36.9)

3.50

3.90

9.50

0.7

2.4

110

95.8

0.81

7

4c (32.8)

0.18

3.63

0.53

1.9

36.4

125

84.6

8

4f(49.6)

0.44

23.40

0.90

1.7

16.7

125

97.9

—

9

5c (56.0)

0.85

4.88

1.50

5.5

63.2

128

15.9

—

10

5f(43.8)

0.18

27.10

0.40

2.0

25.4

123

29.5

—

11

6d(5)

8.05

0.81

—

—

133

100

—

12

6a (5)

8.36

0.4S

-

-

131

100

—

"General conditions: Al/M molar ratio 1000; 20 °C; 1 hour, 700 mL toluene. ^Determined by GC. ^Determined by GPC. determined by DSC. ''The oligomers were determined by GC, GC-MS.

146

W. Zhang etal

not follow Schulz-Floiy rules. Note that the selectivity of the oligomer was very low. In addition, the obtained PE was confirmed to be low molecular weight oligomers possessing small amount of w-butyl branches (the branching degree about 2 w-butyls per 1000 methylenes) in the main chain. At 10 atm ethylene pressure, the palladium complexes showed moderate polymerization activity, and the addition of the PPh3 led to the rapid decrease of activity. 4. CONCLUSIONS A series of late-transition metal complexes containing 2-earboxylate-6~ iminopyridine were synthesized and tested for ethylene polymerization and oligomerization. Upon treatment with MAO, these complexes exhibited the high or moderate activities. The ligand environment affected toward the polymerization behavior for all the complexes, and the higher pressure could lead to the higher activity for these complexes except the cobalt complexes. Addition of PPI13 had little effect toward the ethylene reactivity for iron and cobalt complexes. The oligomers produced by iron complexes were linear aolefins predominantly, and polymers obtained in some cases were linear polymeric a-olefins. Addition of PPh3 as auxiliary ligand led to much higher catalytic activity than that without PPh3 for nickel complexes, but the selectivity of a-olefm of oligomers was very low. Palladium complexes showed much lower activity than the other corresponding analogues. Acknowledgements We are grateful to the National Natural Science Foundation of China for financial supports under Grant No.20473099. Referenees [1] (a) L.K. Johnson, CM. Killian, M. Brookhart, J. Am. Chem. Soc. 117 (1995) 6414; (b) CM. Killian, D.J. Tempel, L.K, Johnson, M. Brookhart, J. Am. Chem. Soc. 118 (1996) 11664; (c) D.P. Gates, S.A. Svejda, E. Onate, C M. Killian, L.K. Johnson, P.S. White, M. Brookhart. Macromolecules 33 (2000)2320. [2] (a) G.PJ. Britovesk, V.C Gibson, B.S. Kimberly, P.J. Maddox, S. J. McTarvish, G.S. Solan, A. J. P. White, D. J. Williams, Chem. Commun. (1998) 849; (b) D.G. Musaev, R.D.J. Froese, K. Morokuma, New J. Chem. 119 (1997) 6177; (c) CM. Killian, L.K. Johnson, M. Brookhart, Organometallies 16 (1997) 2005. [3] (a) X. Tang, W.-H. Sun, T. Gao, J. Hou, J. Chen, W. Chen, J. Organomet. Chem. 690 (2005)1570; (b) W.-H. Sun, X. Tang, T. Gao, B. Wu, W. Zhang, and H. Ma, Organometallies 23 (2004) 5037.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

147

22

Ligand Effect in Syndiospecific Styrene Polymerization and Ethylene/Styrene Copolymerization by Some Nonbridged HalfTitanocenes Containing Anionic Donor Ligandi Hao Zhang and Kotohiro Nomura* Graduate School of Materials Science, Nara Institute of Science and Technology, 89165 Takayama, Ikoma, Nara 630-0101, Japan

Abstract Ligand effects in syndiospecifie styrene polymerization and ethylene/styrene copolymerization by half-titanoeenes of the type, Cp'Ti(L)Cl2 [Cp' = Cp, Cp*, *BuCsH4; L = O-2,6-*Pr2C6H3, N=C*Bu2, Cl], have been explored in the presence of MAO. The catalytic activities in the styrene polymerization with a series of the Cp* analogues increased in the order: OAr > Cl > N=C*Bu2. The catalytic activity, styrene incorporation as well as the microstrueture were affected by both Cp' and L in the ethylene/styrene copolymerization. 1. INTRODUCTION Nonbridged half-titanocenes containing anionic donor ligand of the type, CpTi(L)X 2 (Cp' = cyclopentadienyl group; L = anionic donor ligand such as OAr, NR25 N=PR3, N=CR2 etc.; X = halogen, alkyl etc.; R = alkyl, aryl etc.), are one of the promising candidates as the efficient catalysts for precise olefin polymerization [1-18], because this type of complex catalysts recently displayed unique characteristics as olefin polymerization catalysts producing new polymers that had never been prepared by conventional catalysts. We reported that the aryloxo analogue of the type, Cp'TiCl2(OAr), exhibited high catalytic activities for both olefin polymerization [5,6] and syndiospecific styrene polymerization [19]. These catalysts exhibited unique characteristics for

148

H. Zhang andK. Nomura

copolymerization of ethylene with a-olefm [20] as well as with styrene [21], and revealed that an efficient catalyst for desired polymerization can be modified by the substituents on Cp*. We also reported recently that ethylene/styrene copolymerization took place in a living manner when Cp*TiCl2(N=C*Bu2) (1) was chosen as the catalyst [22], whereas an efficient styrene incorporation was achieved when the aryloxide analogue, Cp*TiCl2(O-2,6-iPr2C6H3) (2) was used as the catalyst [21,22]. These results clearly indicated that anionic donor ligand plays an important key role for the copolymerization behavior and styrene incorporation. Since we also presented that the catalytic activities and molecular weights for the resultant syndiotactic polystyrenes (SPSs) were highly dependent upon the anionic donor ligand employed in the styrene polymerization [19], we explored the more detaiLln this paper, we wish to introduce detailed results for effect of anionic donor ligand in both the styrene polymerization and ethylene/ styrene copolymerization with a series of aryloxide and ketimide analogues (Chart 1). 2. EXPERIMENTAL All experiments were carried out under a nitrogen atmosphere in a Vacuum Atmospheres drybox unless otherwise specified. Anhydrous grade toluene (Kanto Chemical Co., Inc.) was transferred into a bottle containing molecular sieves (mixture of 3A, 4A 1/16, and 13X) under nitrogen stream in the drybox, and was used without further purification. Styrene of reagent grade (Kanto Chemical Co., Inc.) was stored in a freezer after passing through an alumina short column under N2 in the dry box. Cp'TiClzfN^Bua) [Cp' = Cp* (1), Cp = (5)] [22,23], CpTiCyO-^e-'PraCsHs) [Cp' = Cp (6), (tert-BuCsH4 (4), Cp* (2)] [5,6] were prepared according to the previous reports. Toluene and AlMe3 in ordinary MAO [PMAO-S, 9.5 wt% (Al) toluene solution, Tosoh Finechem Co.] were removed under reduced pressure (at ca. 50 °C, and then heated at >100 °C for 1 h) in the drybox to give white solids. Detailed polymerization procedures and isolation procedures were according to our previous reports [19,21,22], and molecular weights and molecular weight distributions for resultant polyethylenes were measured by gel permeation ehromatography (Tosoh HLC-8121GPC/HT) with polystyrene gel column (TSK gel GMHHR-H HT X 2, 30 cm x 7.8 mni(|> ID), ranging from <102 to <

22. Homo- and Capotymerizatian ofStyrene with Ethylene by Half-Titanocenes

149

2 J x i o 8 MW) at 140 °C using o-dichlorobenzene containing 0.05 wt/v% 2,6-diferl~butyl-;>-cresol as solvent. The molecular weight was calculated by a standard procedure based on the calibration with standard polystyrene samples. 3. RESULTS AND DISCUSSION 3.1. Syndiospecific styrenepolymerization by Cp'TiCl2(L) - MAO catalysts. Table 1 summarizes the results for styrene polymerization with a series of Cp*TiCla(L) (1-3) in the presence of MAO at various polymerization temperatures. Both the catalytic activities and the Mw values for resultant syndiotactic polystyrenes (SPS) were influenced by the anionic donor ligand employed, and the activity at 70 °C increased in the order 0-2,6- 'P^CgHj (2) > Cl (3) » N=C*Bu2 (1). The observed activities increased at higher temperature as observed in our previous reports [19,24]. Moreover, the Mw value for resultant SPS was also dependent upon the anionic donor ligand employed, and the value increased in the order (at 70 °C): 2 > 3 > 1. It was revealed that the *BuCp-aryloxide analogue (4) showed remarkable catalytic activities, suggesting that the effective catalyst for the desired polymerization can be tuned by modification of the cyclopentadienyl fragment [19]. Moreover, the Mw values for resultant polymers by 4 were lower than those by the Cp* analogue 2, probably due to the different dominant chain transfer step (confirmed) between the Cp*- and Cp-aryloxide analogues [19]. It also tuned out that the activity by the Cp-ketimide analogue (5) was lower than the Cp* analogue (1) whereas both the Cp-aryloxide analogue (6) and the Cpchloride analogue (7) showed exceptionally higher catalytic activities than the Cp* analogues (1-3), and the Mw values by 5 were higher than those by 1. Based on the above results, it is thus clear that the substituents on both the cyclopentadienyl and the anionic ancillary donor ligands play an important key role for the catalytic activity and molecular weight for resultant polymer in syndiospecific styrene polymerization. 3.2. Ethylene/styrene copolymerization by using Cp 'TiCljfL) - MAO catalysts. To explore the effect of anionic ancillary donor ligand toward the catalytic activity, styrene incorporation as well as copolymerization behavior, three Cp* analogues, Cp*TiCl2(L) [L = N=C'Bu2 (1), OAr (2) and Cl (3)], were chosen for the ethylene/styrene copolymerization in the presence of MAO cocatalyst. The results at 25 °C are summarized in Table 2. The copolymerization by the ketimide analogue 1 took place in a living manner poly(ethylene-co-styrene)s exclusively with narrow molecular weight distribution {MJMn = 1.18) [22],

150

if. Zhang and K. Nomura

although the homopolymerization of ethylene nor styrene did not proceed in a living manner. The highly efficient styrene incorporation was observed in the eopolymerization using the aryloxide analogue (2), and the resultant copolymers possessed uniform composition confirmed by GPC, DSC thermograms, C Table 1. Effect of anionic donor ligand in syndiospeclfic styrene polymerization by Cp'TiG 2 (L) [Cp' = Cp*, L = N=C*Bu2 (1), OAr (2, Ar = ^fi-^CsHj), Cl (3); Cp" = *BuC5H4, L = OAr (4); Cp' = Cp, L = OAr (6% Cl (7)] - MAO catalyst systems." temp.

Cp'.L

MJM*

activity" /DC

xW4

Cp*, N=C'Bu2 (1)

25

63

lg.3

2.3

Cp*, N=CBu 2 (1)

40

81

20.9

2.3

Cp*, N=C'Bu2 (1)

55

140

22.2

2.1

Cp*, N=C'Bu2 (1)

70

222

19.1

2.1

Cp*, OAr (2)

25

190

24.3

2.4

Cp*, OAr (2)d

40

285

26.8

2.6

Cp*, OAr (if Cp*, OAr (if

55

1640

53.1

2.5

70

3600

49.0

2.2

Cp*,Cl(3)

25

210

25.0

2.2

Cp*, Cl (3)d

40

320

36.2

2.3

Cp*, Cl (3)d

55

666

33.2

2.3

d

70

1970

24.8

2.5

'BUC5H4, OAr (4)

25

3140

17.8

1.5

'BuCsH,, OAr (4)

40

7920

10.2

1.6

'BuCjH,, OAr (4)

55

12280

5.3

2.9

(

BuC5H4, OAr (4)

70

7000

3.4

3.7

Cp,OAi(6f

40

1000

5.7

2.1

Cp*, Cl (3)

Cp»OAr(6) d

55

4130

5.8

2.0

Cp, OAr (6f

70

15300

4.0

2.5

Cp, Cl (7)d

40

15800

6.7

2.8

Cp, Cl (7)d

55

17500

4.8

2.7

d

70

15300

3.3

2.4

Cp,Cl(7)

"Conditions: complex 2.0 p,mol or 1.0 ixmol, MAO (prepared by removing AlMej and toluene from PMAO) 3.0 mmol, styrene + toluene total 30 mL, 100 mL scale autoclave; bActivity in kg-polymer/mol-Ti"h; CGPC data in o-dichlorobenzene vs polystyrene standards; dCited from reference 19.

NMR spectrum and GPC/FT-IR [21,22]. No resonances ascribed to (head-totail) styrene repeating unit were seen in the 13C NMR spectrum in the copolymer prepared by 1, whereas the peaks due to two, three styrene repeating

22, Homo- and Copolymerization ofStyrene with Ethylene by Half-Titanocenes

151

units were seen for the polymer prepared by 2. Note that the polymerization by 3 under the same conditions afforded a mixture of polyethylene and syndiotactic polystyrene. These results clearly indicate that the anionic donor ligand directly affects toward the catalytic activity, styrene incorporation as well as the microstructure in the copolymer. Table 2. Effect of anionie donor ligand In ethylene-styrene copolymerization by Cp'TiClaCL) [L = N=C<Bu2(l), OAr (2), Cl (3); Cp'= 'BuCp, L = OAr (4); Cp'= Cp, L = N=CBu 2 (§)] - MAO catalyst systems.* cat.

Cp'.L

(umol)

composition I:%) b

poly(ethylene-co-styrene)s or PE, SPSb

E-S

PE

SPS

activity11

st. cont

M/xlO" 4

MJMne

1 (2.0)

Cp*, N=CBu 2

>99

trace

trace

400

7.4

9.5

1.18

2(2.0)

Cp*, OAr

>99

trace

trace

500

31.9

5.73

1.62

86.8

13.2

250

>99

5.85

1.26

—

0.29

2.69

3(2.0)

Cp*, Cl

trace

4(1.0)

'BuCp, OAr

>99

trace

trace

6300

47.6

13.6

1.68

5 (10,0)

Cp, N=C*Buz

<5

trace

trace

<1

--

--

--

"Conditions: catalyst 2.0 pmol, 10.0 umol, MAO (prepared by removing AlMej and toluene from PMAO) 3.0 mmol, ethylene 6 atm, styrene 10 mL, styrene + toluene total 30 mL, 10 min; ''Based on a mixture of PE, SPS and copolymer. (acetone insoluble fraction); "Activity in kgpolymer/mol-Ti-h; dStyrene content (mol%) estimated by : H NMR; eGPC data in odiehlorobenzene vs polystyrene standards.

It should also be noted that the Cp-ketimide analogue, CpTiCl2(N=C*Bu2) (S), showed the negligible catalytic activity under the same conditions, whereas the 'BuCp-aryloxide analogue (4) showed the highest catalytic activity and the remarkable efficient styrene incorporation. These results clearly indicate that the substituent on Cp strongly affects the ethylene/styrene copolymerization behavior. Based on above results, it is thus clear that the substituents on both the cyclopentadienyl and the anionic ancillary donor ligand directly affect the catalytic activity, styrene incorporation as well as the microstructure in the copolymer for ethylene/styrene copolymerization. Acknowledgements Z.H. expresses his thanks to JSPS for a postdoctoral fellowship (P04129). K.N. expresses his thanks to Tosoh Finechem Co. for donating MAO (PMAO-S). References [1] K. Nomura, Trend in Organometallic Chemistry 4 (2002) 1.

152

H. Zhang andK, Nomura

[2] K. Nomura, in: S. G. Pandalai (Ed.); Recent Research Development in Polymer Science, Transworld Rseareh Network; Kelara, India, 2005, pi05, [3] K. Nomura, in: Rita Skoda-Foldes (Ed.); Advances in Organic Chemistry (On Line), Bentham Science Publisher Ltd., New York, 2006, accepted. [4] D. W. Stephan, Organometallics 24 (2005) 2548. [5] K. Nomura, N. Naga, M. Miki, K. Yanagi, A. Imai, Organometallics 17 (1998)2152. [6] K, Nomura, N. Naga, M. Miki, K. Yanagi, Macromolecules 31 (1998) 7588, [7] S. A. A. Shah, H. Dom, A. Voigt, H. W. Roesky, E. Parisini, H. -G. Schmidt, M. Noltemeyer, Organometallics 15 (1996) 3176. [8] S. Doherty, R. J. Errington, A. P. Jarvis, S. Collins, W. Clegg, M. R. J. Elsegood, Organometallics 17 (1998) 3408. [9] L. R. Sita, R. Babcock, Organometallics 17 (1998) 5228. [10] J. Richter, F. T. Edehnann, M. Noltemeyer, H. -G. Schmidt, M. Schmulinson, M. S. Eisen, J. Mol. Catal. A 130 (1998) 149. [11] D. W. Stephen, J. C. Stewart, F. Guerin, R. E. v. H. Spenee, W. Xu, D. G. Harrison, Organometallics 18 (1999) 1116. [12] R. Vollmerhaus, P. Shao, N. J. Taylor, S. Collins, Organometallics 18 (1999)2731. [13] W. P. Kretschmer, C. Dijkhuis, A. Meetsma, B. Hessen, J.H. Teuben, Chem, Commun. (2002) 608. [14] K. Nomura, K. Fujii, Organometallics 21 (2002) 3042. [15] K. Nomura, K. Fujii, Macromolecules 36 (2003) 2633. [16] P.-J. Sinnema, T. P. Spaniol, J. Okuda, J. Organomet. Chem. 598 (2000) 179. [17] J. McMeeking, X. Gao, R. E. v. H. Spenee, S. J. Brown, D. Jerermic, USP 6114481(2000). [18] K. Nomura, K. Fujita, M. Fujiki, J. Mol. Catal. A 220 (2004) 133. [19] D.-J. Byun, A. Fudo, A. Tanaka, M. Fujiki, K. Nomura, Macromolecules 37(2004)5520. [20] K. Nomura, K. Oya, Y. Imanishi, J. Mol. Catal. A 174 (2001) 127. [21] K. Nomura, H. Okumura, T. Komatsu, N. Naga, Macromolecules 35 (2002)5388. [22] H. Zhang, K. Nomura, J. Am. Chem. Soc. 127 (2005) 9364. [23] S. Zhang, W. E. Piers, X. Gao, M. Parvez, J. Am. Chem. Soc. 122 (2000) 5499. [24] K. Nomura, K. Fujita, M. Fujiki, Catal. Commun. 5 (2004) 413.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

153 153

23

Titanium and Zirconium Complexes Bearing a Trialkoxoamine Ligand: Synthesis and Olefin Polymerization Activity Padmanabhan Sudhakar, and Govindarajan Sundararajan Department of Chemistry, Indian Institute of Technology, Madras-600036, India

Abstract The effect of catalyst symmetry over the stereoregularity of the polyolefins obtained and the mechanism of the polymerization were studied with various aminoalcohol based titanium and zirconium catalysts having C3 and pseudo-C, symmetries. These precatalysts in combination with MAO polymerized 1-hexene in a controlled manner. The isotactic polyhexene obtained from the Cj-symmetric titanium catalyst (1-T1C1) had molecular weight of around 46500 (pdi = 1.3) and the zirconium analogue (1-ZrCl) had the molecular weight of 53000. The hemi-isotactic polymer from the pseudo-C,symmetrie titanium catalyst (2-TiQ) had the molecular weight of around 617000 (pdi = 1.3) and that of zirconium analogue (2-ZrCl) had molecular weight of 626000. The catalysts prepared from a 50:50 mixture of the ammotriols also polymerized 1-hexene and the bimadal nature of the GPC traces of the polyhexenes obtained suggests that these catalysts act independently in the mixture and also imply the absence of polymeryl transfer between the catalytic centers. In all cases, the individual catalysts apparently retain their original symmetry (Cj or Cs) avoiding the formation of aggregates or polymeric forms.

1. Introduction Recently, the study of non-metallocene complexes in the area of olefin polymerization has gained much attention because some of these catalysts are able to polymerize a-oleflns in a living manner [1 ]. Previous communications from our group have demonstrated that aminodiolate titanium precatalysts of Cj and C, symmetry can be used for effecting transformation reactions (from vinyl-addition to metathesis) and for controlled polymerization of 1-hexene [2].

154

P. Sudhakar and G. Sundararajan Ph

OH

Ph

OH

1-H3(CJ

f

O ^ ,'A-O I Ci M = Ti: 1-TiCI (C3S M = Zr. 1 -ZrCI (CJ

Ph

OH

Ph

A

OH

2-H 3 (C,j

^

Ph 7y |

I Cl M = Ti: 2-TiCI (CJ M = ZK 2-ZrCI (CJ

Figure 1, Ligands and precatalysts used in this study

We were interested in extending these studies for precatalysts containing aminotrisalkoxyligands of higher symmetry like Cj. Use of such polydentate ligands for olefin polymerization ligands is rare but not unavailable [3]. In continuance of our earlier studies, we synthesized aminotrialkoxy ligands having C3 and pseudo-Cs symmetry for complexation with titanium and employed the catalysts the polymerization of ethylene, a-olefms and cyclic-olefins [4]. This paper mainly presents in detail the synthesis of the C3 and pseudo-C, titanium and zirconium precatalysts (Figure 1) and their ability to polymerize 1-hexene.

2, Results and Discussion 2.1. Synthesis of precatalysts The required precatalysts 1-TiCl and 2-TiCl containing ligands 1-H3 and 2-Hj, were synthesized according to literature reported [4, 5]. In order to test the possible occurrence of polymeryl transfer among the reacting metal centers we also prepared the mix catalyst, synthesized by deliberately mixing pure 1-H3 and 2-H3 ligands in equal amounts, followed by treatment with Ti(O'Pr)4 and acetyl chloride. The zirconium analogs (1-ZrO and 2-ZrCl) of titanium catalysts were prepared by the addition of tri sodium salt of the aminotriols to ZrCU. Though 1-ZrCl and 2-ZrCI did not crystallize well, their structural nature could be established by NMR spectroscopy and elemental analyses. The shift in the 'H and 13C NMR signals from those in the corresponding spectra of the ligands indicated the formation of the complexes. The CH2-N protons showed a shift of 0.4 - 0.7 ppm indicating the possibility of N coordination to titanium as reported elsewhere for the similar type of compounds [5]. 2.2. Catalytic activities in polymerization of 1-hexene using 1-TiClor

2-TiCl/MAO

With chlorobenzene as solvent [6], we could observe tangible polymerization activities, attributable to the optimal dielectric constant of the medium. In the case of 1TiCl, maximum activity was seen when the Al/Ti ratio was around 200 and for 2-TiCl and the mix catalysts the optimal Al/Ti ratio was around 500. The polyhexenes obtained using these catalyst systems are isotactic. The percentage of isotacticity was found to be higher for polymers obtained from 1-TiCl (80-85%) than for the polyhexene from 2TiCl (55-65%). The mix precatalysts produced polyhexenes where the % isotacticity

23. Titanium and Zirconium Complexes Bearing a Trialkoxoamine Ligand

155

depended on the relative % of 1-TiCl and 2-TIO catalysts. Thus a catalyst mixture containing equal amount of 1-TiCl and 2-TiCl, yielded polyhexene having a maximum isotacticity of 70% and mixtures of other ratios of the precatalysts influenced the isotacticity of the polyhexene accordingly, implying that symmetry of the catalysts does play an important role in determining the stereoregularity of the polymers obtained (Table 1), Table 1. Polymerization of 1 -hexene with different ratios of 1 -TiCl and 2-TiCl a % 1-TiCl /2-TiCl 100/0 75/25 50/50 50/50* 25/75 0/100

Activity1* 2.2 2.2 2.0 2.0 2.3 2.5

Fraction 1 pdi 1.5 27530 1.4 26500 1.3 29300 1.3 31500 1.3 28700 -

M,'

Fraction 2 pdi 36BG0Q 1.3 436000 1.2 1.2 443000 412000 1.2 1.4 450000

Isotacticity4 (% mmmm) 85 77 71 72 68 62

"Catalyst = 2x10"* moles, Al/Ti = 200,1 -hexene = 5 mL, Time = 24 h, Solvent = 10 mL at -10 °C; bkgPH/mole catalyst-h; determined from GPC in THF using narrow polystyrene standards; % mmmm determined by 13C NMR spectra; e50/50 mixture of catalysts as generated.

For both the catalyst systems, the percentage isotacticity of the polymers obtained increased with decrease in temperature of the reaction, may be because the growing polymer chain, gains the required corrformational stability at low temperature [7a]. Similar behavior observed by Odian [7b] for hexene polymerization was rationalized by alluding to tight coordination of the propagating center, catalyst counterion and monomer, that loosens at high temperatures to allow some mis-insertions, thereby decreasing the stereoregularity of the polyolefin. In case of polymers from mixed catalysts, where both the catalysts retain their individual identities, a decrease in the percentage mmmm value was seen. The polymerization activity of 1-TiCI and 2-TiCl increased slightly when the polymerization temperature was increased to 50 °C from ambient temperature (30 °C) but the activity decreased drastically when the temperature was lowered to 0 °C and dipped a little more when the temperature was lowered to -10 °C. The similarity in behavior of these catalysts was evident from the activation energies calculated for the polymerization of 1-hexene. (Ea C3 = 32 kJ/mol and Ea Cs= 30 kJ/mol) [2, 8]. The slight decrease in activity at high temperatures observed could be due to the deactivation of the active species and the drastic decrease at low temperatures could be due to the slow activation of catalyst to generate the necessary active species. The molecular weights of the polymers obtained with 1-TiCI increased nearly ten-fold from 5500 for room temperature polymerization to 34000 when the temperature was lowered to 0 °C and increased further to 46500 when the temperature of polymerization was brought down to -10 °C. In comparison, the changes in the molecular weight of the polyhexenes obtained with the mix were not as striking upto 0 °C, but when the polymerization temperature was decreased to -10 °C the molecular weight increased ten-fold same as that of 1-TiCI but still ten times lower than the molecular weight of the polyhexene obtained with 2-TiCl at -10 °C (Figure 2). The progressive increase in molecular weights of the polymers with time is shown as the GPC traces in Figures 2a and 2b. It was also seen that as the polymerization temperature increased the molecular

156

P. Sudhakar and G. Sundararajan

weights of the polymers decreased suggesting a high rate of chain termination at elevated temperatures, predominantly through p-hydride elimination. Polymerization with the deliberately mixed 1-TiCl and 2-TiCl symmetric precatalysts (50:50) also yielded same amount of polymers with the characteristics same as that of the mix catalysts. An overlay of the GPC traces of the polymers obtained from catalysts 1-TiCl and 2-TiCl, on the bimodal curve obtained for the polymers from mix catalyst performed at -10°C, does suggest the presence of a mixture of two different homopolymers in the latter system. A simple manipulation of the bimodal curve seen in Figure 2c, i.e. breaking it down to two independent curves, gives the following data; the composite bimodal curve has an Mn = 67300 (pdi = 4.8) while the component curves give values of Mn = 676180 (pdi = 1.12) and Mn = 48 ti 46890 (pdi = 1.2). These values compare well with 24 those obtained independently for the polyhexenes ."2 obtained from catalysts 1-TiCI and 2-TiCI, entry 1 in Table 2, suggesting that the catalyst prepared from the mixture of ligands, is a mixture of catalysts 1-TiCI and 2-TiCI, with no evidence for the formation of aggregates or polymeric forms. We also prepared the Crsymmetric aminotriolate titanium ben^l complex, by bezylating 1-TiCI and 2TiCl using Bn-MgBr, activated with MAO and 'h Elution Time/min studied the polymerization activities of 1 hexene. We find the activity of 1TiBn or 2-TiBn /MAO; molecular weights and the stereoregularity of the polyhexenes obtained are as 0 10 20 30 0 10 20 30 Elution time/ min Elution time/ min same as that of 1TiCl or 2-TiCl Figure 2. GPC curves of polyhexene obtained in 48, 24, 12, 6 hours with (a) 1-TiCl (b) 2-TiCl precatalysts at -10 ° C and (c) polyhexene obtained /MAO. with (i) 2-TiCl, (ii) 1-TiCl and (Hi) mix precatalysts at -10 °C after 48 h. 2.3. Catalytic activity in polymerization of 1-hexene using zirconium precatalysts 1ZrCl or 2-ZrCl/MAO The activity and the molecular weight of the polymers obtained are comparable with the titanium catalysts (Table 2). The polyhexene obtained using the mixture of the catalysts also showed a bimodal type of GPC curve indicating the absence of polymeryl transfer among these catalysts and both these catalysts behave individually in solution. The stereoregularity of the polymers obtained are same as that of the titanium analogues (80-85% isotactic). In all these cases, the major terminations are p-hydride elimination

23. Titanium and Zirconium Complexes Bearing a Trialkoxoamine Ligand

157

and with a minor chain transfer to aluminum, confirmed from the 'H NMR of the obtained polyhexenes. Table 2. Polymerization of 1 -hexene with 1-TiCl, 2-TiCl, 1-ZrCI, 2-ZrCl and mix catalysts a Time

00 1 2

24

3 4

48 24

l-TiCl(Cj) pdf M.h

2-TiCl (pseudo-Q

46500 1.3 27530 1.3 l-ZrCl(Cj) 53000 1.2 36500 1.3

617000 1.3 450000 1.4 2-ZrCl (pseudo-Q 626000 1.2 420000 1.3

M?

pdf

Mix (C3&Q)

M? 67300 49200 Mix (C3& 226000 118000

% Isotacticit/ c. Mix

pdf

q»

4.8 5.S C.) 4.1 5.2

85 82

65 62

75 72

85 85

62 62

72 70

" Catalyst = 2x10"* moles, Al/TI = 200,1 -hexene = 5 mL, Time = 24 h, Solvent = 10 mL at -10 °C; b'cdetennined from GPC in THF using narrow polystyrene standards; "*% mmmm determined by 13C NMR spectra.

2,4. Mechanism of the polymerization With regard the mechanism of olefin polymerization, it is well-established that the active metal center, in addition to being ligated by atoms of the ligand, should be cationic, attached to the growing polymer chain and must have a vacant coordination site to accommodate the incoming olefin. In that context, precatalysts 1-TiCl, 2-TiCl, 1-ZrCI and 2-ZrCI could be activated for olefin polymerization by abstraction of the chloride group by MAO to give a monocationic species. Though the metal center so generated will lack the required vacant coordination site, removal of a ligated oxygen atom by MAO, to facilitate the approach of monomer hexene, also cannot be ruled out. Similar suggestions have been mooted by Eisen [9a] to explain the reactivity of a C3~ symmetric zirconium catalyst attached to three benzamidinate ligands., by Nomura [9b] on ostensibly similar titanium(IV) compounds of triaryloxoamine ligands, by delinking a metal-oxygen bond prior to initiating ethylene polymerization and Bruno [9c] offers a similar route for styrene polymerization by titanium compound containing tripodal aryloxide ligands in presence of MAO. Our attempts to follow the nature of activation of the 1-TiCl or 2-TiCl by MAO using 47Ti NMR has not been very informative as is normal for all distorted octahedral complexes of titanium [10]. A rudimentary MM2 energy minimization done for the cationic species derived from 1-TiCl, with dimeric hexene unit attached and with one of the three alkoxy arm delinked, yielded a structure that is clearly less open for polymer chain growth compared to the two structures produced by a similar process for cationic species 2-TiCI. The vastly open environment at the metal center for the latter offers clues to the extremely high molecular weight polymers formed from 2-TiCI and the relatively low molecular weight polymer derived from 1-TiCI. We are investigating further the structure-activity relationships in this family.

3. Conclusion We have synthesized aminotriolate based titanium and zirconium catalysts having C3 and pseudo-C, symmetry, which polymerized 1 -hexene in a controlled manner. The

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Ci symmetric catalysts produced Isotactic polymer and the pseudo-C, symmetric catalysts produced hemi-isotaetic polymers suggesting that as the symmetry of the catalyst increases, the stereoregularity of the polymers increases. Even when the catalyst was prepared from a mixture of ligands, the catalysts generated acted independently and produced polymers with different chain lengths ruling out polymeryl transfer between the catalyst centers. We have tentatively proposed the cleavage of a metal-oxygen bond by MAO, to facilitate the approach of monomer. Acknowledgments We thank Department of Science and Technology, New Delhi, India for research grant (No.: SP/S-l/G-08/99) and Reliance Industries Limited for financial support. References [1] For reviews see (a) G. W. Coates, P. D. Hustad, S. Reinartz, Angew. Chem., Int. Ed. Engl. 41 (2002) 2236-2257. (b) V. C. Gibson, S. K. Spitzmesser, Chem. Rev. 103 (2003) 283-316. [2] (a) R. Manivannan, G. Sundararajan, W. Kaminsky, Macromol. Rapid Commun. 21 (2000) 968-972. (b) R. Manivannan, G. Sundararajan, Macromolecules 35 (2002) 7883-7890. [3] Y. Kim, E. Hong, M. H. Lee, J. Kim, Y. Han, Y. Do, Organometallics 18 (1999) 36-39. [4] (a) P. Sudhakar, V. Amburose, M. Nethaji, G. Sundararajan, Organometallics 23 (2004) 4462 - 4467. (b) P. Sudhakar, G. Sundararajan, Macromol. Rapid Commun. 26 (2005) 1854-1859. [5] W. A. Nugent, R. L. Harlow, J. Am. Chem. Soc. 116 (1994) 6142-6148. [6] The choice of the solvents was based on the literature reports. See, (a) J. D. Scollard, D. H. McConville, J. Am. Chem. Soc. 118 (1996) 10008-10009. (b) L. C. Liang, R. R. Schrock, W. M. Davis, J. Am. Chem. Soc. 121 (1999) 5797-5798. [7] (a) J. Ewen, J. Am. Chem. Soc. 104 (1984) 6355 - 6364. (b) X. Zhao, G. Odian, A. Rossi, J. Polym. Sci. Part A; Polymer Chemistry 38 (2000) 3802-3811. [8] W. Kaminsky, R. Werner, Metalorganic Catalysts for Synthesis and Polymerization- Recent results by Ziegler-Natta and Metallocene Investigations. W. Kaminsky. Eds: Springer-Verlag: Berlin Heidelberg, 1999, pp. 170. [9] (a) C. Averbuj, E. Tish, M. S. Eisen, J. Am. Chem. Soc. 120 (1998) 8640-8646. (b) W. Wang, M. Fujiki, K. Nomura, Macromol. Rapid Commun. 25 (2004) 504507. (c) L, Michalczyk, S. Gala, J. W. Bruno, Organometallics 20 (2001) 55475556. [10] (a) T. J. Boyle, T. H. Alamond, E. R. Meehenbier, Inorg. Chem. 36 (1997) 3293. (b) A. Foris, Magn. Reson. Chem. 38 (2000) 1044-1046.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

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Stereoselective Polymerization of Styrene by FI Catalysts Kenji MicMue," Mitsuhiko Onda/ Makoto Mitani," and Terunori Fujita" "R&D Center, Mitsui Chemicals, Inc., 580-32 Nagaura, Sodegaura, Chiba 299-0265, Japan, Mitsui Chemical Analysis & Consulting Service, Inc., 580-32 Nagaura, Sodegaura, Chiba 299-0265, Japan

Abstract Styrene polymerization behavior of group 4 metal bis(phenoxy-imine) complexes, MCl2{1f-l-[C(H)=N(phenyl)]-2-O-3-'Bu-C6H3}2 [M = Ti (1); M = Zr (2); and M = Hf (3)], was studied with dried methylalumoxane (DMAO) activation. When polymerization conditions were explored for 1, premixing of the catalyst had a pronounced effect on enhancing activity. When performance among the different group 4 metals was compared at Tp = 80 °C, activity and Tm decreased in the following order; 1 (30 kg/(mol-h), 267 °C) > 2 (7 kg/(mol-h), 218 °C)> 3 (0.3 kg/(mol-h), 214 °C). 1. INTRODUCTION In our efforts to develop new high activity non-Cp molecular catalysts, we found that group 4 transition metal complexes bearing phenoxy-imine ligands (named FI Catalysts) are notable high performance olefin polymerization catalysts [1,2]. Since some non-Cp group 4 metal catalysts are known to serve as stereo-selective polymerization catalysts for styrene [3], styrene polymerization with FI Catalysts was examined as an extension of our continuing research interests into this intriguing catalyst family [1,4].

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K. Michiue et al.

2. EXPERIMENTAL Materials. The FI Catalysts used for this study were prepared according to the methods described in our previous papers (Figure 1): (1) [5], (2) [6], (3) [7]. Toluene employed as a polymerization solvent (Wako Pure Chemical Industries, Ltd.) was dried over AI2O3 and degassed by bubbling with dried nitrogen gas, Styrene (Wako Pure Chemical Industries, Ltd.) was washed with 0.1N aqNaOH to remove the polymerization inhibitor and dried over MgSO4, then distilled under vacuum. The purified styrene was stored in the refrigerator and used within a week. Dried methylalumoxane (DMAO, 1.32 M in toluene) was prepared by evaporating commercially available MAO (Albemarle, 1.2 M in toluene) in vacuo to remove the remaining trimethylaluminum, and dissolved again in toluene, then stored in the refrigerator.

M=Ti(1),Zr(Z), Hf(3)

Figure 1. FI Catalysts employed in stereospeeifie styrene polymerization.

Polymerization Procedure. Styrene polymerization for Table 1 was carried out in a 40 mL Schlenk flask equipped with a stirring bar. A prescribed amount of toluene was introduced into the nitrogen-purged flask and magnetically stirred at polymerization temperature. For the reactions (run 1 and 2), 5 mmol of DMAO and 20 mL of styrene were added to the Schlenk flask in that order, then thermally equilibrated at the polymerization temperature for 10 min. 0.02 mmol of precatalyst solution in toluene was injected into the DMAO/toluene/styrene solution in the Schlenk flask to start the reaction. For the reactions (run 3 and 4), in which the precatalyst and DMAO were premixed, 0.02 mmol of precatalyst solution in toluene and 5 mmol of DMAO solution in toluene were first mixed at 20 °C and stirred for 13 min for aging. The polymerization was started by adding the premixed precatalyst/MAO solution to the toluene in the reaction vessel. The total volume of the toluene in the reaction mixture was 10 mL for all runs. After 60 min., sec-butyl alcohol was added to terminate the polymerization, Styrene polymerization for Table 2 was carried out in a 500 mL glass reactor equipped with a propeller-like stirrer. A prescribed amount of toluene was introduced into the nitrogen-purged reactor and thermally equilibrated at the polymerization temperature with stirring (600 rpm). 12.5 mmol of DMAO solution in toluene and 0.05 mmol of the precatalyst complex solution in toluene were added in that order, then kept 10 min for aging with stirring at

24, Stereoselective Polymerization ofStyrene by FI Catalysts

161

polymerization temperature. Polymerization was started by introducing styrene (100 mL) and the mixture was stirred. The total volume of the toluene in the reaction mixture was 30 mL for all runs. After 60 min, sec-butyl alcohol was added to terminate the polymerization. For workup of polymer samples, the resulting mixture was added to acidified methanol, filtered and washed with methanol, then dried in a vacuum oven at 130 °C for 10 h. For polymer extraction, the polystyrene samples were dissolved in methylethylketone (MEK) at 20 °C, and insoluble fractions were separated by filtration, then washed thoroughly with MEK and dried in a vacuum oven at 130 °C for 10 h. Analytical Procedures. Molecular weights (Mw and Mn) and molecular weight distributions (MWD) of polystyrenes were determined using a Waters GPC2000 gel permeation chromatograph equipped with four TSKgel columns (two sets of TSKgelGMH6HT and two sets of TSKgelGMH r HTL) at 140 °C using polystyrene calibration. o-Dichlorobenzene was employed as a solvent at a flow rate of 1.0 ml/min. Calorimetrie measurements of the polystyrenes were determined by differential scanning calorimetry (DSC) with a Perkin-Elmer DSC-7 differential scanning calorimeter. The polymer samples were first heated at a rate of 20 °C/min from 20 °C to 300 °C, held at this temperature for 5 min, and cooled to 30 °C at a rate of 10 °C/min. The polymer samples were held at this temperature for 5 min, and then reheated to 300 °C at a rate of 10 DC/min. The reported values of the melting temperature (Tm) relate to the second heating scan. 3. RESULTS AND DISCUSSION J. 1, Effect of polymerization conditions Effect of polymerization conditions on styrene polymerization was investigated for 1 (Table 1). At first glance, it seemed that 1/DMAO was inactive in syndiospecific styrene polymerization at conditions indicated in run 1 and 2, for virtually no crystalline PS (MEK insoluble polymers) was obtained (ran 1 and 2). However, premixing of the complexes with DMAO prior to starting the polymerization reaction led to an increase in activity. When Tp was further increased under the premixing conditions, activity was further increased. The MEK insoluble polymers exhibited distinct Tm at 271 °C ( run 3 and 4), indicative of highly sPS, and showed MWD of 2.9 with unimodal shape characteristics of single-site catalysis.

162

K. Michiue et al. Table 1. Polymerization of Styrene with 1/MAO Systems'* MEK-insoluble fraction Premix

Temp.

Yield

11

Content

Activity6

MBd (MWD)

Tm

3

(°C)

(xlO )

(min)

CC)

(wt %)

1

-

20

0.198

Trace

-

-

-

2

-

40

0.2S0

Trace

-

-

-

3

13

40

0.537

49

13.26

109.1 (2.9)

271

4

13

60

0.5S9

55

16.04

100.6 (2.9)

271

"Polymerization conditions: 10 mL toluene, 20 mL styrene, 0,02 mmol preoatalyst, 5 mmol DMAO, 60 min. Percentage of content in methylethylketone insoluble fraction. "Activity calculated for MEK-insoluble fraction, Units: kg polymer/{niol Ti-h). TNTumber average molecular weight determined by GPC.

3,2. Comparison of polymerization performance among different group 4 metals. Following up the results by Ti-FI Catalyst (1), polymerization performance by Zr-(2) and Hf-FI Catalysts (3) was also examined and compared with that of 1 (Table 2). For these studies, to obtain a sufficient quantity of products for analysis, experiments were conducted on a larger scale than that of Table 1 with conditions sufficient for sPS formation, which was anticipated from the results obtained in Figure 1, i.e., elevated polymerization temperature and premixing of the catalyst conditions. Polymerization by 1/DMAO in these conditions also gave highly syndiotactic PS with a Tm of 268 °C ([rr] = 80 % by 13C-NMR; run 1). On the other hand, when polymerization by 2/MAO was examined, 20% of the MEK insoluble polymer that exhibited a Tm of 218.0 °C ([rr] = 73 % by 13CNMR) was obtained (run 2). More interestingly, 3/DMAO also gave a crystalline polymer that exhibited a Tm of 214 °C ([rr] = 60 % by 13C~NMR; run 3). Previously, no hafnium catalysts that afford sPS have been reported, thus this is the first time to report a hafnium catalyst with an ability to control stereoregularity in a syndiospecific manner. Mn for the sPS by 2 and 3/DMAO are smaller than that of 1/DMAO, and both of the GPC traces showed unimodal shape with narrow MWD, indicative of single-site catalysis.

24. Stereoselective Polymerization ofStyrene by Fl Catalysts

163

Table 2. Polymerization ofStyrene with Fl Catalyst/MAO Systems* MEK-insoluble fraction Complexes

Time

Yield

1

Content " Activity0

(nun)

(g)

(wt%)

3.293

45

M/(MWD) 3

TM

(xlO )

fC)

29.5

53.9 (2.6)

268

1

1

60

2

2

60

1.763

20

6.9

7.2(1.7)

218

3e

3

600

16.099

6

0.4

7.3(1.5)

214

"Polymerization conditions: 30 mL toluene, 100 mL styrene, 0.05 mmol precatalyst, 12.5 mmol DMAO, 80 °C, 60 min. *Percentage of content in methylethylketone insoluble fraction, eActivity calculated for MEK-insoluble fraction, Units: kgpolymer/(mol-Metal-h), ''Number average molecular weight determined by GPC. "0.5 mmol precatalyst, 125 mmol DMAO.

4. CONCLUSION Styrene polymerization by Fl Catalyst (Ti, Zr, Hf)/MAO systems was demonstrated. Higher Tp and premixing of the complex with DMAO are effective to increase activity for sPS formation. It was revealed that all of the group 4 metal catalysts have an ability to afford sPS in a single-site nature (MWD <3.0). Acknowledgements We thank Mitsui Chemical Analysis & Consulting Service, Inc. for NMR, GPC and DSC measurements and analyses. References [1] T. Fujita, Y. Tohi, M. Mitani, S. Matsui, J. Saito, M. Nitabaru, K. Sugi, H. Makio, T. Tsutsui, Eur. Pat. Appl. 0 874 005 (1998) [2] For reviews, see, (a) H. Makio, N. Kashiwa, T. Fujita, Adv. Synth. Catal. 344 (2002) 477-493. (b) Y. Suzuki, H. Terao, T. Fujita, Bull. Chem. Soc. Jpn. 76 (2003) 1493-1517. (c) N. Matsukawa, S. Ishii, R. Furuyama, J. Saito, M. Mitani, H. Makio, H. Tanaka, T. Fujita, e-Polymers (2003), art. no.-021. (d) M. Mitani, J. Saito, S. Ishii, Y. Nakayama, H. Makio, N. Matsukawa, S. Matsui, J. Mohri, R. Furuyama, H. Terao, H. Bando, H, Tanaka, T. Fujita, Chem. Rec. 4 (2004) 137-158. (c) K. Michiue, S. Matsui, Y. Yoshida, T. Fujita, Recent Res. Devel. Chem. 2 (2004) 191-226.

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[3] For reviews, see, (a) R. Po and N. Cardi, Prog Polym Sci. 21 (1996) 47-88. (b) N. Tomotsu, N, Ishihara, T, H. Newman, M, T, Malanga, J. Mol. Catal., A, 128 (1998) 167-190. (c) N. Tomotsu andN. Ishihara, Studies in Surface Science and Catalysis 121 (1999) 269-276 (Science and Technology in Catalysis 1998), (d) J Schellenberg, N. Tomotsu, Prog. Polym. Sci. 27 (2002) 1925-1982. (e) Y. Qian, J. Huang, M. D. Bala, B. Lian, H. Zhang, H. Zhang, Chem, Rev. 103 (2003) 2633 -2690. (f) N. Ishihara, In Progress and Development of Catalytic Olefin Polymerization, Eds.; Technology and Education Publishers: Tokyo, (2000) 121-128. [4] K. Michiue, M. Onda, T. Fujita, Jpn. Pat, Appl. (Appl. No. 2005-122384). [5] S. Matsui, Y. Tohi, M. Mitani, J. Saito, H. Makio, H. Tanaka, M. Nitabaru, T. Nakano, T. Fujita, Chem. Lett. (1999) 1065-1066. [6] S. Matsui, M. Mitani, J. Saito, Y. Tohi, H. Makio, N. Matsukawa, Y. Takagi, K. Tsuru, M. Nitabaru, T. Nakano, H. Tanaka, N. Kashiwa, T. Fujita, J. Am, Chem. Soc. 123 (2001) 6847-6856. [7] (a) J. Saito, M. Onda, S. Matsui, M, Mitani, R. Furuyama, H. Tanaka, and T. Fujita. Macromol. Rapid Commun. 23 (2002) 1118-1123. (b) A. V. Prasad, H. Makio, J. Saito, M. Onda, T. Fujita. Chem, Lett. 33 (2004)250-251.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

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Synthesis of Bis(imino)pyridine Complexes of Group 5 Metals and Their Catalysis for Polymerization of Ethylene and Norbornene Yuushou Nakayama, Naoaki Maeda, Takeshi Shiono Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Higashi-Hirashima 739-8527, JAPAN

Abstract A series of niobium(III) and tantalum(lll) complexes having 2,6-bis{l(arylimino)ethyl}pyridine ligands was synthesized. These complexes activated with TJu-modified methylaluminoxane (MMAO) exhibited moderate activity for ethylene polymerization to give linear polyethylene with broad molecular weight distribution. These complexes were also moderately active for ringopening metathesis polymerization of norbornene in combination with AlEtj or MMAO. 1. INTRODUCTION 2,6-Bis(imino)pyridine derivatives have been proved to be excellent ancillary ligands for a variety of transition metal complexes as olefin polymerization catalysts [1-7]. We have also reported that bis(imino)pyridine-molybdenum complexes were good catalyst precursors both for ethylene polymerization and for ring-opening metathesis polymerization (ROMP) of norbornene [8]. These molybdenum complexes were found to afford polynorbomene with high cis content, when they were activated with 'Bu-modified methylaluminoxane (MMAO). In this study, we applied the bis(imino)pyridine ligands for complexes of Group 5 metals such as niobium and tantalum, and studied their catalytic behaviors for ethylene polymerization and for ROMP of norbornene.

166

Y. Nakayama et al.

2. EXPERIMENTAL 2.1. General Remarks Because of the air and moisture sensitivity of organometallic compounds, all the manipulations were carried out under a pure and dry argon atmosphere, using standard Schlenk techniques. Solvents such as tetrahydrofuran and nhexane were distilled from Na/K-benzophenone under argon prior to use. Toluene and dimethoxyethane was purified by distillation from sodiumbenzophenone. NMR and mass spectra were measured on a JEOL JNM-400 (400 MHz) and JEOL JMS-SX102A spectrometers, respectively. Elemental analysis was performed on PE 2400 Series II CHN/O Analyzer. Molecular weights of the poly(norbornene)s were determined by gel permeation chrornatography (TOSOH SC-8010) calibrated by using standard poly(styrene)s, and using chloroform as eluent at 40 °C. GPC measurements of polyethylene were performed on Waters C150 by Mhon-polyolefin Co. Ltd., Japan. 2,6Bis{l-(arylimino)ethyl}pyridines were prepared according to a literature [9]. 2.2. Synthesis of[2,6-Bis{l-arylimino}ethyl]pyridine]MCk (1—5, M = Nb, Ta) NbCl3(DME) [10] (0.545 g, 1.88 mmol, DME = 1,2-dimethoxyethane) and 2,6-bis{l-(2,6-diisopropylphenylimino)ethyl}pyridine (0.996 g, 2.07 mmol) were dissolved in THF (90 mL) and the solution was refluxed for 12 h. The resulting suspension was cooled to room temperature and evaporated to dryness. The residue was washed with hexane (45 mL x 2) followed by drying in vacuo. [2,6-Bis{l-(256-diisopropylphenylimino)ethyl}pyridine]NbCl3 (1) was obtained as a purple powder (0.918 g, 72 %). Anal. Calcd. for CaaH^NsNbCI,: C, 58.20; H, 6.37; N, 6.17. Found: C, 58,11; H, 6.44; N, 6.20. MS(EI) mlz 679 (M4), Complexes 2—4 were synthesized and isolated in a manner similar to that of 1. [2,6-Bis{l-(2,6-diethylphenylimino)ethyl}pyridine]NbCl3 (2): a purple powder (0.454 g, 72 %) Anal. Calcd. for C29H35N3NbCl3: C, 55.74; H, 5.65; N, 6.72. Found: C, 54.52; H, 5.74; N, 7.54. MS(EI) mlz 623 (M4). [2,6-Bis{l-(2,6dimethylphenylimino)-ethyl}pyridine]NbCl3 (3): a purple powder (0.399 g, 75 %) Anal. Calcd. for C25H27N3NbCl3: C, 52.79; H, 4.78; N, 7.39. Found: C, 49.89; H, 5,54; N, 6.59. MS(EI) mlz 567 (M+). [2,6-Bis{l-(2,4,6trimethylphenylimino)ethyl}pyridine]NbCl3 (4): a purple powder (0.546 g, 80 %) Anal. Calcd. for Cz7H3iN3NbCl3: C, 54.34; H, 5.27; N, 7.04. Found: C, 53.57; H, 5.42; N, 6.83. MS(EI) mlz 595 (M+). [2,6-Bis{l-(2,6dimethylphenylimino)ethyl}pyridine]TaCl3 (5): a pink powder (0.502 g, 69 %) Anal. Calcd. for C33H43N3TaCl3: C, 51.54; H, 5.64; N, 5.46. Found: C, 52.42; H, 6.62; N, 5.21. MS(EI) mlz 767 {Wf). 2.5. Polymerization of Ethylene with the Bis(imino)pypridine Complexes of Niobium and Tantalum A typical procedure: To a complex (0.02 mmol) in dry toluene was added a given amount of an aluminum compound and then the mixture was stirred for 5

25. Synthesis and Catalysis ofBis(imino)pyridine Complexes of Group 5 Metals

167

min at room temperature. The solution was degassed and ethylene (1 atrn) was introduced to start the polymerization. After the prescribed time, the polymerization mixture was quenched with a large amount of methanol containing a small amount of hydrochloric acid. The precipitates were centrifuged and dried in vacuo. GPC measurements were performed. 2.4. ROMP ofNorbornene with the Bis(imino)pypridine Complexes of Niobium and Tantalum A typical procedure: To a complex (0.02 mmol) in dry toluene was added a given amount of an aluminum compound and then the mixture was stirred for 5 min. After norbornene was added at a stroke, the solution was stirred at ambient temperature. The polymerization mixture was quenched with a large amount of methanol containing a small amount of hydrochloric acid. The precipitates were centrifuged and dried in vacuo. NMR and GPC measurements were performed. 2.5. X-ray structure analysis of the complex 2 A single crystal of 2 sealed in a glass capillary under an argon atmosphere were mounted on a Rigaku RAXIS RAPID Imaging Plate area detector with MoKoc radiation at 123 K. Indexing was performed three oscillations which were exposed for 3.0 min. The camera radius was 127.40 mm. Readout was performed in the 0.10 mm pixel mode. The data were corrected for Lorentz and polarization effects. The structures were solved by directed method and refined by full-matrix least-squares methods. _ Crystallographic data for the structural analysis of 2 have been deposited with the Cambridge Crystallographic Data Centre, CCDC no. 293790. Copies of this information may be obtained free of charge from The Director, CCDC, 12 Union Road, Cambridge CB2 1EZ, UK (fax: +44-1223-336-033 or e-mail: [email protected] or http://www.ccdc.cam.ac.uk). 3. RESULTS AND DISCUSSION 3.1. Synthesis ofbisfimmo)pyridme complexes of niobium and tantalum The bis(imino)pyridine ligands were reacted with a stoichiometric amount of MC13(DME) (M = Nb, Ta; DME = 1,2-dimethoxyethane) in THF to give bis(imino)pyridine complexes of niobium(III) and tantalum(III) 1—S in reasonable yields (eqn. 1). X-ray crystallography of 2 revealed its meroctahedral structure (Fig. 1), although the crystal did not have very good quality.

Y. Nakaycma et at

168

MCI3{DME)

1:M = Nb, R = 'Pr, R'= H 2: M = Nb, R = Et, R' = H

3: M = Nb, R = Me, R' = H 4: M = Nb, R = R' = Me 5: M = Ta, R = 'Pr, R' = H

3,2. Polymerization of ethylene by the ninhium and tantalum complexes The complexes 1—5 exhibited ethylene polymerization activity in the presence of MMAO as a cocatalyst. Among the niobium complexes 1—4, the bulkiest complex 1 showed the highest activity. With increasing [A1]/[M] ratio, the activity of these complexes increased, Fig 1. Molecular structure of 2. while the molecular weight of the resulting polymer decreased. The resulting polyethylenes had very broad molecular weight distributions suggesting multiplicity of the active species, and high melting points indicating linear structure. The activity of 1 is higher than those of diene-niobium complexes (~38.7 kgPE/mol'h) [11], and comparable to those of chelating triphenolato complexes (~90 kgPE/mol'h) [12]. The tantalum complex 5 was less active than the corresponding niobium complex 1.

>ft

Table 1. Ethylene Polymerization with Niobium and Tantalum Complexes 1—5/MMAO. complex [A1]/[M] activity ~M? UJM? ^T 1 4 (kgPE/mol-h) (/10 ) fC) 1 100 4.25 11.3 140.3 15 1 500 133.2 0.33 4.3 70 135.2 2 100 0.48 106.9 6 129.8 500 15 2 0.70 17.9 137.6 100 5 3 127.4 500 22 3 32.4 0.42 100 4 133.6 4 128.2 500 11 4 1.29 13.8 5 132.3 100 5 0.31 6.0 130.2 500 18 Conditions; catalyst = 0.02 mmol, ethylene = 1 atm, solvent = 30 mL of toluene, temp. = r.t, time = 10 min.a)Dtermined by GPC. b) Dtermined by DSC.

25. Synthesis and Catalysis ofBis(imino)pyridine Complexes of Group 5 Metals

169

3.3. ROMP qfnorbornene by the niobium and tantalum complexes The complexes 1—5 also catalyzed polymerization of norbomene in the presence of aluminum cocatalysts. In spite of ethylene polymerization activity of the complexes 1—5 activated with MMAO, no vinyl-addition polymerization of norbomene proceeded and only ROMP of norbornene occurred even in the presence of MMAO or MAO. As observed in ethylene polymerization, bulkier niobium complex showed higher activity. The polydispersity indexes MyJMn of the resulting polymers were close to 2, indicating these systems are single-site catalysts for the ROMP of norbornene. The tantalum complex S exhibited higher activity than that of the corresponding niobium complex 1, but still less active than alkylidenetantalum complexes having aryloxide or arenethiolate ligands [13]. The molecular weight of the resulting polymer decreased with polymerization time, indicating secondary metathesis reaction of the polymer main chain. When the complexes 1—5 were activated with AlEt3, no cisftmns specificity was observed . The niobium complex 1 activated with MMAO gave fr<ms-rich polynorbomene, while the use of MMAO for the tantalum complex 5 slightly increased cis-specificity. Table 2. ROMP of Norbomene Catalyzed by the Complex 1—5. cocat. complex [A1]/[M] time yield trans-cant. * MJM* (mol/mol) % 104 % (h) AlEtj 1 73 1 34 1.96 24 55 1 40 100 17 1.70 24 MMAO 75 21 3.22 24 2 17 AlEt3 45 21 28 2.56 AlEtj 24 50 3 4 34 AlEt 3 38 1.93 24 49 S 71 A1E% 16 2.23 3 52 13 2.25 52 75 AlEt 3 6 5 A1E% 86 12 11 2.84 52 5 AlEt 3 82 24 8 3.98 53 S 3.21 100 24 5.2 5 MAO 40 46 42 100 3 16.4 4.73 42 5 MMAO 100 24 99 12.4 6.92 41 S MMAO Conditions: catalyst = 0.02 mmol, [monomer]o/[catalyst] = 100 mol/mol, solvent = 1 mL of toluene, temp. = r.t. a ' Determined by GPC calibrated with standard polystyrenes. b^ Determined by'HNMR.

4. CONCLUSIONS A series of bis(imino)pyridine complexes of tantalum and niobium were synthesized by the reaction of MCl3(DME) (M = Nb, Ta) with bis(irnino)pyridines in THF. These bis(imino)pyridine complexes showed moderate activities for ethylene polymerization upon activation with MMAO to

170

Y. Nakayama et al.

yield linear polyethylene. The niobium and tantalum complexes were also moderately active for ROMP of norbornene in the presence of AlEt3, MMAO, or MAO. The bulkiest niobium complex having 2,6-diisopropyl substituents exhibited the highest activity among the studied niobium complexes in both cases. Acknowledgements The authors are grateful to Tosoh Fineehem Co. for supplying the cocatalysts. References [I] B.L. Small, M. Brookhart and A.M.A. Bennett, J. Am. Chem. Soc, 120 (1998)4049-4050. [2] G.J.P. Britovsek, V.C. Gibson, B.S. Kimberley, P.J. Maddox, S.J. McTavish, G.A. Solan, A.J.P. White and DJ. Williams, Chem. Commun., (1998)849-850. [3] D. Reardon, F. Gonan, S. Gambarotta, G. Yap and Q. Wang, J. Am. Chem. Soc, 121(1999)9318. [4] D.P. Gates, S.A. Svejda, E, Onate, CM. Killian, L.K, Johnson, P.S. White and M. Brookhart, Macromolecules, 33 (2000) 2320-2334. [5] M.A. Esteruelas, A.M. L6pez, L. M6ndez, M. Olivan and E. Oflate, Organometallics, 29 (2003) 395-406. [6] B.L. Small, M.J. Carney, D.M. Holman, C.E. O'Rourke and J.A. Halfen, Macromolecules, 37 (2004) 4375-4386. [7] Y. Nakayama, K. Sogo, H. Yasuda and T. Shiono, J. Polym. ScL: Part A: Polym. Chem., 43 (2005) 3368-3375. [8] K. Hiya, Y. Nakayama and H. Yasuda, Macromolecules, 36 (2003) 79167922. [9] GJ.P. Britovsek, M. Bruce, V.C. Gibson, B.S. Kimberley, P.J. Maddox, S.M.S.J. McTavish, C. Redshaw, G.A. Solan, S. Stromberg, A.J.P. White and DJ. Williams, J. Am. Chem. Soc, 121 (1999) 8728-8740. [10] EJ. Roskamp and S.F. Pedersen, J. Am. Chem. Soc, 109 (1987) 65516553. [II] K. Mashima, S. Fujikawa, Y. Tanaka, H. Urata, T. Oshiki, E. Tanaka and A. Nakamura, Organometallics, 14 (1995) 2633-2640. [12] C. Redshaw, D.M. Homden, M.A. Rowan and M.R.J. Elsegood, Inorg. Chim. Ada, 358 (2005) 4067-4074. [13] K.C. Wallace, A.H. Liu, J.C. Dewan and R.R. Schrock, J. Am. Chem. Soc, 110(1988)4964-4977.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

171

26 Ethylene Polymerization with an Anilinonaphthoquinone-Ligated Nickel Complex Mitsuhiro Okada, YuushouNakayama, and Takeshi Shiono* * Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Himshima, 739-8527, JAPAN.

Abstract An anilinonaphthoquinone-ligated nickel complex activated with tris(pentafluorophenylborane) system showed high activity for ethylene polymerization at 40 °C under atmospheric pressure and gave polyethylene with long chain branches and short chain branches. The activity was decreased by lowering the polymerization temperature accompanied by the increase in molecular weight. The number of the chain branches was also decreased according to the polymerization temperature. The polyethylene produced at 20 °C had only methyl branch formed by chain work, whereas polyethylene produced at 0 °C had no branches. 1. INTRODUCTION Since Brookhart and co-workers discovered a-diimine complexes of nickel and palladium, late-transition-metal complexes have received much attention for polymerization catalysts[l-6]. Polymerization temperature significantly affects the activity, molecular weight and the structure of the polymer obtained in ethylene polymerization catalyzed by nickel complexes [7-10]. We have previously reported that an anilinonaphthoquinone-ligated nickel complex 1 activated with tris(pentafluorophenylborane) showed high activity for ethylene polymerization. The polyethylene obtained by this catalytic system at 40 °C possessed short chain branches formed by chain walk via p-hydride elimination /reinsertion/ migration Kgure 1 Nickel complex 1

172

MOkadaetal.

and long chain branches. The long chain branches should have been formed by the copolymerization of ethylene with macromonomer formed via p-hydride elimination[ll]. In this study, we report the effects of polymerization temperature on polymerization activity, molecular weight and the structure of the polymers produced in the present system. 2. EXPERIMENTAL Materials, All manipulations were carried out under a nitrogen atmosphere using standard Schlenk techniques. All solvents were refluxed with sodium/benzophenone or calcium hydride and distilled before use. The complex 1 was prepared according to the method reported previously[11 ]. Polymerization Procedure, Polymerization was performed in a 100-mL glass reactor equipped with a magnetic stirrer and carried out by the following method. At first, the reactor was charged with a prescribed amount of toluene. After the toluene was saturated with an atmospheric pressure of ethylene, polymerization was started by adding the toluene solution of 1 pre-activated with 4 equiv. B(CgFs)3 at 80 °C for 30 min. Polymerization was conducted for a certain time keeping the ethylene pressure constant and terminated with methanol. The polymers obtained were adequately washed with methanol and dried under vacuum at 60 °C for 6 h. Analytical Procedures. Molecular weights and molecular weight distributions of polyethylenes obtained were determined by gel permeation chromatography (GPC) with a Waters 150CV at 140 °C using o-diehlorobenzene as a solvent. The 13C NMR spectra of the polyethylenes were measured at 120 °C on a JEOL GX 500 spectrometer operated at 125.65 MHz in the pulse Fourier-transform mode. The pulse angle was 45* and about 4000-8000 scans were accumulated in pulse repetition of 5.0 s. Sample solutions were prepared in 1,1,2,2tetrachloroethane-^ up to 10 wt-%. The central peak of the solvent (74.47 ppm) was used as an internal reference. Differential scanning calorimetry (DSC) curves of the samples were recorded on a Seiko DSC-220 under nitrogen with a heating rate of 10 °C/min from 25 "C to 170 "C. 3. RESULTS AND DISCUSSION Ethylene polymerization was conducted by 1 at 0, 20 and 40 °C, of which results are summarized in Table 1. Polymerization proceeded irrespective of the temperature. The molecular weight of the polymer obtained drastically increased at low temperature although the polymerization activity decreased. The Tm value determined by DSC rose 113 °C to 144 °C as the polymerization temperature decreased from 40 °C to 0 DC, which indicates that the structure of

173

26, Ethylene Polymerization with am Anilinonaphthoqumone-Ligated Ni Complex

polyethylene obtained was depended on the polymerization temperature. The 13 C NMR spectra of the polyethylenes are shown in Figure 2. Table 1. Polymerization of Ethylene by an Anilinonaphthoquinone-Ligated Nickel Complex I 1 Time

T

Entry No.

Temp. /°C

/min

1

40

7

1,320

18,000

3.95

113

2

20

7

957

324,000

2.88

127

3

0

28

249

1,160,000

4.11

144

Activity13

MWDC

'm

/°c d

* Polymerization conditions: toluene = 150 ml, Revolution rate = 600 RPM, Ni = 25 (J,mol, B(C6Fj)3 = 100 jitnol, Ni complex and B(C6FS)3 were premixed at 80 °C for 30 min. b Activity in kg-polyethylene / (mol-Nrh). e Mn and MWD determined by GPC using polystyrene etandard. Determined by DSC.

45

40

35

30

25

20

IS

10

13

Figure 2. C NMR spectra of polyethylenes obtained at 40 °C (a), 20 °C (b), 0 °C (o).

We have previous reported that the polyethylene produced at 40 °C had short chain branches and long chain branches (Figure 2a)[ll]. Decreasing the

174

MOkadaetal.

polymerization temperature to 20 °C gave the polyethylene with only methyl branch which is formed by chain walk via p-hydride elimination / reinsertion / migration (Figure 2b), and the polyethylene obtained at 0 °C had no branches detected by 13C NMR (Figure 2c). The effect of polymerization temperature on the polymer structure can be interpreted as follow. At low polymerization temperature, P-hydride elimination is suppressed more than propagation, which causes to decrease the short chain branches as well as vinyl-terminated polymers via P-hydride elimination. Consequently the long chain branch formed by the copolymerization of ethylene with the vinyl terminated polymers also decreases and linear polyethylene is obtained. 4. CONCLUSIONS The anilinonaphthoquinone-ligated nickel complex 1 activated by B(C6F5)3 conducted ethylene polymerization with high activity and gave branched and linear polymers depending on the polymerization temperature. Acknowledgments The authors are grateful to Tosoh-Finechem Co., Ltd., for donating Isoper-E solution of B(CfiF5)3. The NMR measurement was made at the Natural Science Center for Basic Research and Development (N-BARD), Hiroshima University. Reference [I] L. K. Johnson, C. M. Killian, M, Brookhart, J, Am. Chem. Soc. 117 (1995) 64145415. [2] G. J. P. Britovsek, V. C. Gibson, D. F. Wass, Angew. Chem. Int. Ed. 38 (1999) 428447. [3] S. D. Ittel, L. K. Johnson, M. Brookhart, Chem. Rev. 100 (2000) 1169-1203. [4] L. S. Boffa, B. Novak, Chem. Rev. 100 (2000) 1479-1494. [5] S. Mecking, A. Held, F. M. Bauers, Angew. Chem. Int. Ed. 41 (2002) 544-561. [6] ¥. C. Gibson, S. K. Spitzmesser, Chem. Rev. 103 (2003) 283-315. [7] S. A. Svejda, L. K. Johnson, M. Brookhart, J. Am. Chem. Soc. 121 (1999) 1063410635. [8] D. P. Gates, S. A. Svejda, E. Oflate, C. M. Killian, L. K. Johnson, P. S. White, M. Brookhart, Macromolecules 33 (2000) 2320-2334. [9] F. M. Zhu, W. Xu, X. Liu. S. Cin, J. Appl. Polym. Chem. 84(2002) 1123-1132. [10] H. Zou, F. M. Zhu, Q. Wu, J. Y. Ai, S. A. Lin, J. Polym. Sei. Part A: Polym. Chem. 43 (2005) 1325-1330. [II] M. Okada, T. Ikeda, T. Shiono, Preprints of The 8th SPSJ International Conference (2005) 509.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

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27

Ring Opening Metathesis Polymerization of Norbornene Catalyzed by V(CH2SiMe3)2(N~2,6Me2C6H3)(N=C'Bu2). In situ generation of the Vanadium-Alkylidene Kotohiro Nomura* and Junji Yamada Graduate School of Materials Science, Nara Institute of Science and Technology, 89165 Takayama, Ikoma, Nara 630-0101, Japan

Abstract (Arylimido)(ketimide)vanadium dialkyl complex, V(CH2SiMe3)2(N-2,6Me2C6H3)(N=CfBu2) (1) could be prepared by reaction of the diehloride with two equivalent of LiCH2SiMe3 in high yield, and the complex was identified by 'H, I3C, S 1 V NMR spectra. Complex 1 showed relatively high catalytic activity for ring-opening metathesis polymerization of norbornene, and the activity increased upon the addition of PMej. Remarkable increase in the activity was observed at higher temperature, and these results suggest the formation of the vanadium-alkylidene complex, V(CHSiMe3)(N-2,6-Me2C6H3)(N=C'Bu2)(PMe3), which could be isolated upon heating the C6D6 solution containing 1 and PMe3. 1. INTRODUCTION Olefin metathesis such as ring-opening metathesis polymerization (ROMP), ring-closing (RCM) and cross metathesis (CM) reaction [1-4] have attracted considerable attention due to the promising possibility for application not only to polymer synthesis but also to synthesis of valuable organic compounds [1-4], Successful examples have been demonstrated by molybdenum [5], ruthenium [6,7], however, the examples with vanadium complexes have been limited. We recently reported that ROMP of norbornene (NBE) by (ArN)V(CH2Ph)2(O-2,6-'Pr2C6H3) (Ar = 2,6-Me2C6H3) took place to afford ultra high molecular

176

K. Nomura andJ. Yamada

weight polymer with a unimodal molecular weight distribution [8]. We also communicated that vanadium(V)-alkylidene, (ArN)V(=CHSiMe3)(L)(PMe3) (2, L = N=C'Bu2), has been isolated from (ArN)V(CH2SiMe3)2(L) (1) by othydrogen elimination, and 2 initiated ROMP of NBE [9]. Since the dialkyl analogue, 1, which could be prepared in high yield from the dichloro analogue, also initiated ROMP of NBE, yielding high molecular weight polymers with unimodal molecular weight % distributions, we explored the ^-P---, 1 + PMe3 ROMP by 1 (in situ generation ^J~~^f **" system) for more detail (Scheme 1). 1: (ArN)V(CH2S!Me3)2(N=CfBu2) 2. EXPERIMENTAL Scheme 1 All experiments were carried out under a nitrogen atmosphere in a Vacuum Atmospheres drybox or using standard Schlenk techniques. All chemicals used were reagent grade and were purified by the standard purification procedure. Anhydrous-grade benzene, diethyl ether and «~hexane (Kanto Kagaku Co., Ltd,) were transferred into a bottle containing molecular sieves (a mixture of 3A, 4A 1/16, and 13X) in the drybox under N2, and were then passed through an alumina short column before use. Polymerization grade toluene was distilled from sodium and benzophenone, stored over a sodium/potassium alloy in drybox, and then passed through an alumina short column before use. 3. RESULTS AND DISCUSSION The reaction of (ArN)VCl2(L) with LiCH2SiMe3 in R-hexane afforded (ArN)V(CH2SiMe3)2(L) (1) in high yield (95 %), and the complex was identified by ]H-, 13C-, 51V-NMR spectra and elemental analysis [9], The coordination of PMe3 to 1 was not observed even by addition of excess amount (7.0 equiv.) at 25 °C, and this observation might be due to the steric hindrance of rather bulky CH2SiMe3 group around the V metal center. The complex 1 initiated ROMP of NBE in toluene (Table 1), and the activity increased especially upon addition of PMe3 (runs 3-6). This might be due to the more efficient formation of the vanadium-alkylidene (2) in the reaction mixture. However, the activity decreased upon further addition (run 7), and this can be assumed that the coordination of PMe3 into the vanadium metal center retards the propagation (coordination of NBE), leading to lower activities. Note that the observed catalytic activity (in the presence of PMe3) notably increased at higher temperature, and the higher activity was observed even at 80 °C whereas the significant decrease in the activity due to the decomposition was observed if RuCla(CHPh)(PCy3)2 (Cy = cyclohexyl) was used in place of 1 (run 17). The activity was also affected by the NBE concentration, and the

27. ROMP ofNorbornene Catalyzed by r(CH2SiMe^(N-2,6-Me2CsH3)(N=C?Bui)

177

resultant polymer possessed rather broad but unimodal molecular weight distributions probably due to the rapid propagation compared to the slow initiation. This assumption can be realized from the fact that the resultant polymer by 2 possessed narrow molecular weight distribution and that the observed activity by 2 was much higher than those by 1 (run 16). Table 1. ROMP of NBE with V(CH2SiMe3)2(NAr)(N=CtBua) (1), or RuCl2(CHPhXPCy3)2 (Ru). a run

complex

NBE

NBE

P/Vc

temp.

time

TONd

rc

/h

...

25

1

1306

0.89

3

25

6

1.6

4.24

0.89

...

50

6

0.5

1 (20.0)

4.24

0.89

3

50

3

61

5

1 (10.0)

4.24

0.89

3

50

6

140

6

1 (10.0)

4.24

0.89

3

50

6

150

7

1 (10.0)

4.24

0.89

5

50

6

66

80

6

6.8

(umol)

/mmol

1

Ru(l.O)

2

b

2.12

cone. 0.22

1 (10.0)

2.12

3

1 (20.0)

4

MJMf 4

xlO" 54

1.7

26.1

5.4

48.1

4.0

g

1 (20.0)

4.24

0.89

...

9

1 (20.0)

4.24

0.89

3

80

1

61

10

1 (10.0)

4.24

0.89

3

80

3

378

60.3

5.4

f

87

3.2

11

1 (10.0)

2.12

0.44

3

80

3

212

12

1 (10.0)

1.06

0.22

3

80

3

101

97

3,0

13

1 (10.0)

2.12

0.44

5

80

3

40

47

3.0

14

1 (10.0)

4.24

0.89

5

80

3

183

69

3.7

15

1 (10.0)

4.24

0.89

5

80

6

285

16

2(1.Of

2.12

0.22

—

80

1

1583

133

1.4

17

Ru(l.O)

2.12

0.22

—

80

1

350

"Conditions: NBE 1.06-4.24 mmol, toluene. Initial NBE concentration in mmol/mL, cMolar ratio ofPMej/V. d*TON TON = NBE consu consumed (mmol)/V (mmol). BGPC data vs polystyrene standards. 'Completion of polymerization.

Resultant polymer possessed ring-opened structure containing a mixture of cis- and trans- olefmic double bonds, as shown in Figure 1, and the fact was somewhat different from those observed in the ROMP by (ArN)VCl2(O-2,6- AlMe3 catalyst system [8]. This would be assumed as due to the

178

degree of synlanti rotamer (rotational isomer or rotamer) and/or the mode of NBE coordination into the vanadium metal center proposed by the molybdenum-alky lidene catalyst [5]. Taking into account the above results, it is clear that the present catalyst system displays unique characteristic as thermally robust transition metal alkylidene which shows remarkable reactivity toward cyclic olefrns especially at higher temperature.

K. Nomura andJ. Yamada

cis

trans

5.5

5.3

5.1 5 .1

m ppm PP

Figure 1. 'H NMR spectra (CDC13) for ringopened poly(norbomene) prepared by 1 ~ PMe3 (3.0 eq) catalyst.

Acknowledgements This research is partly supported by Tokuyama Science Foundation, and authors express their thanks to Prof. Michiya Fujiki (NAIST) for helpful discussions. J.Y. expresses his thanks to the JSPS for a predoctral fellowship (No. 5042). References [1] R. H. Grubbs (Ed.), Handbook of Metathesis, Wiley-VCH, Weinheim, 2003, Vol. 1-3. [2] E. Khosravi, T. Szymanska-Buzar (Eds.), Ring-Opening Metathesis Polymerisation and Related Chemistry, Kluwer, Dordrecht, 2002. [3] Y. Imamoglu, L. Bencze, (Eds.), Novel Metathesis Chemistry: Well-Defined Initiator Systems for Specialty Chemical Synthesis, Tailored Polymer and Advanced Material Applications, Kluwer, Dordrecht, 2003. [4] M. R. Buehmeiser, Chem. Rev. 100 (2000) 1565. [5] R. R. Schrock, in: R. H. Grubbs (Ed.), Handbook of Metathesis, Wiley-VCH, Weinheim, 2003, Vol. 1, p 8. [6] T. M. Trnka, R. H. Grubbs, Ace. Chem. Res., 34 (2001) 18. [7] S. T. Nguyen, T. M. Trnka, R. H. Grubbs (Ed.), Handbook of Metathesis, Wiley-VCH, Weinheim, 2003, Vol 1, p 61. [8] K. Nomura, A. Sagara, Y. Imanishi, Macromoleeules 35 (2002) 1583. Examples for ROMP by vanadium catalysts were cited therein. [9] J. Yamada, M, Fujiki, and K. Nomura, Organometallics 24 (2005) 2248. Detailed analysis results are shown in the Supporting Information.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

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28

Ethylene/2~Methyl-l-Pentene Copolymerization Catalyzed by Half-Titanocenes Containing Aryloxo Ligand: Effect of Cyclopentadienyl Fragment Kotohiro Nomura* and Koji TtagaM Graduate School of Materials Science, Nara Institute of Science and Technology, 89165 Takayama, Ikoma, Nara 630-0101, Japan

Abstract Efficient incorporation of 2-methyl-l-pentene (2M1P) has been observed in copolymerization of ethylene with 2-methyl-l-pentene (2M1P) using Cp*TiCl2(O-2,6-TJr2C6H3) (1) - MAO catalyst, and the resultant polymers were poly(ethylene-co-2MlP)s that possessed high molecular weights with unimodal molecular weight distributions as well as with uniform 2M1P incorporation. The tert-BuCp analogue, ('BuCsH4)TiCl2(O-2,6-'Pr2CsH3) (2), showed less efficient 2M1P incorporation than 1, whereas 2 showed better 1-hexene incorporation in ethylene/1-hexene copolymerization. The steric bulk in both 2M1P and the cyclopentadienyl fragment thus affected the comonomer incorporation in this copolymerization. 1. INTRODUCTION Evolution of new polyolefins prepared by newly designed polymerization catalysts is one of the most attractive subjects in the field of metal catalyzed coordination polymerization, because new properties that have never been observed by conventional catalysts can be highly expected [1,2] especially by the precise placement of chemical functionality and/or substituent. Only a few examples were reported for copolymerization of ethylene with isobutene (IB) using linked (amide)(cyclopentadienyl)titanium complex catalysts called constrained geometry catalyst [3-4], and the IB content was low (<2.8 mol%) in the copolymerization by [Et(indenyl)2]ZrCl2 - methylaluminoxane (MAO)

180

K. Nomura andK. Itagaki

catalyst even under large IB stoichiornetric excess conditions (TB:ethylene = 4000:1) [5], Examples for efficient synthesis of high molecular weight copolymers with unimodal molecular weight distributions in the copolymerization of ethylene with 1,1-disubstituted a-olefin except IB had thus never been reported so far. Since some nonbridged half-titanoeenes containing anionic ancillary donor ligand of the type, Cp'TiCl2(X) (Cp* = eyelopentadienyl, X = anionic donor ligand), displayed unique characteristics especially in copolymerization of ethylene with a-olefins [6], styrene [7], cyclic olefins [8,9], we thus explored the copolymerization of ethylene with so called "traditionally unreactive" monomers such as 2-methyl-l-pentene (2M1P) by these nonbridged half-titanocenes [10]. Since we communicated that 2-methyl-l-pentene (2M1P) could be successful incorporated in ethylene/2MlP copolymerization using Cp*TiCl2(OAr) (1, Ar = 2,6-'Pr2CsH3) - MAO catalyst under appropriate 2MlP/ethylene molar ratios, in this paper, we wish to introduce our explored results for the copolymerization of ethylene with 2M1P (Scheme 1),

Scheme 1

2. EXPERIMENTAL All experiments were carried out under a nitrogen atmosphere in a Vacuum Atmospheres drybox unless otherwise specified. Anhydrous grade toluene (Kanto Chemical Co., Inc.) was transferred into a bottle containing molecular sieves (mixture of 3A, 4A 1/16, and 13X) under nitrogen stream in the drybox, and was used without further purification. 2-Methyl-l-pentene (TCI) of reagent grade (Kanto Chemical Co., Inc.) was stored in a freezer after passing through an alumina short column under N2 in the dry box. Cp'TiCl2(O-2,6-'Pr2C6H3) [Cp' = Cp* (1), (tert-BuC5H4 (2)] [11] were prepared according to the previous reports. Toluene and AlMe3 in ordinary MAO [PMAO-S, 9.5 wt% (Al) toluene solution, Tosoh Finechem Co.] were removed under reduced pressure (at ca. 50 °C, and then heated at >100 °C for 1 h) in the drybox to give white solids. Detailed polymerization procedures and isolation procedures were according to our previous reports [10], and molecular weights and molecular weight distributions for polymers were measured by gel permeation chromatography (Tosoh HLC-8121GPC/HT) with polystyrene gel column (TSK gel GMHHR-H HT x 2, 30 cm x 7.8 mmcf> ID), ranging from <102 to < 2.8xlO8 MW) at 140 °C

28. Ethylene/2-Methyl-l-pentene Copolymerization Catalyzed by Half-titanocenes 181

using o-dichlorobenzene containing 0.05 wt/v% 2,6-di-ferf-butyl-p-eresol as solvent. The molecular weight was calculated by a standard procedure based on the calibration with standard polystyrene samples. Optimized geometries calculated by molecular mechanics were based on equilibrium geometry at ground state with semi-empirical PM3, geometry optimization, RHF/PM3D, Spartan Pro '04 for Windows (Wavefunetion Inc.). 3. RESULTS AND DISCUSSION Two complexes, Cp'TiCyO^fi-'PraCgHj) [Cp' = Cp* (1), 'BUC5H4 (2)], have been chosen as the catalyst precursors, because these complexes showed better 1-hexene incorporation (lower TE values) than ordinary metallocenes and linked half-titanocenes in ethylene/1-hexene copolymerization [6]. The results under the optimized conditions are summarized in Table 1. It tuned out that the copolymerizations by 1 - MAO catalyst took place with high catalytic activities, and the activity decreased upon increasing the 2M1P concentration and/or upon decreasing ethylene pressure. The resultant polymers were poly(ethylene-co-2MlP)s confirmed by 13C NMR spectra, DSC thermograms (Fm values), and the copolymers possessed high molecular weights with unimodal molecular weight distributions as well as with uniform 2M1P distributions [10]. The 2M1P contents in the resultant copolymers decreased upon increasing the ethylene pressure and/or upon decreasing the 2M1P concentration charged, and the Mn values for resultant copolymers decreased upon increasing the 2M1P contents. A linear relationship between Tm values and the 2M1P contents was observed [10]. These results thus strongly suggest that the copolymerization proceeded with single catalytically-active species. The observed catalytic activities were also affected by Al/Ti molar ratios, whereas the Mn values were independent upon the Al/Ti molar ratios. In contrast, 2M1P contents in the resultant copolymer prepared by 2 were lower than those by 1 under the same conditions, although 2 incorporates 1hexene more efficiently than 1 under the same conditions in ethylene/1 -hexene copolymerization [6]. This may be due to the steric hindrance of tert-buryl group on Cp' against the methyl group in inserted 2M1P, as described below. In order to explore the reason why 2 showed less 2M1P incorporation, the optimized geometries for assumed catalytically-active [cationic Ti(IV) alkyl] species, especially [Cp*Ti(OAr)(2-methyl-2-butyl heptyl)(ethylene)]+ [Cp' = Cp; (1'), 'BUC5H4 (2')] were calculated by molecular mechanics (Figure 1). It was revealed that the Cp* analogue (Figure lb, 1') was more stable than the tert-Bu analogue (Figure la, 2') and the AE value (7.863 kcal/mol) was somewhat large, probably due to the steric bulk between the methyl group in inserted 2M1P and tert-Bu group.

182

K, Nomura amdK. Itaguki

Table 1 Copolymerization of ethylene (E) with 2-methyl-l-pentene (2M1P) by Cp'TiO 2 (0Ar) [Cp' = Cp* (1), 'BuC5H4 (2)] - MAO catalysts." E run cat. 2M1PC yield activity*1 2M1PB MAO/ mmol M/ MJMj 4 3 3 / m xlO" /atm (Al/TiKlO" )" / m o l % no. xlO" /mL (jimol) g 1 — — 2.1 1 (0.5) 49 6 3.0 (6.0) 530 6.36 2 1.5(3.0) 1 (0.5) 11 412 4.94 1.7 6 5 582 1.7 3.0 (6.0) 3 6 1 (0.5) 13 6.98 5 1.7 4.5 (9.0) 4 6 13 3.2 672 8.06 5 1 (0.5) 1(0.5) 1.8 6.0 (12.0) 6 6 13 656 7.87 5 7 1 (0.5) 5.7 1.8 4.5 (9.0) 7.2 480 6 5.76 10 1 (0.5) 353 4 4.24 1.8 4.5 (9.0) 8 5.3 5.0 5 1.9 4.5 (9.0) 223 9 3.3 9.4 4 2.68 10 1 (0-5) 5.5 2(2.0) 1.9 4.0 (2.0) 270 10 2.3 6 0.81 5 226 11 4.3 2(2.0) 3.2 2.0 4.0 (2.0) 0.68 10 6 2.1 4.0 (2.0) 156 12 3.1 2 (2.0) 3.2 0.47 5 4 13 2(2.0) 0.32 4 2.3 4.0 (2.0) 108 1.8 5.1 10 "Conditions: 2M1P + toluene total 30 mL, 2M1P 5.0 or 10.0 mL, MAO (prepared by removing toluene and AlMe3 from ordinary PMAO), 25 °C, 10 min; bMolar ratio; C2M1P charged (mL); Activity in kg-polyrner/mol-Ti-h; e 2MlP in copolymer estimated by C NMR (in benzene-dg/ 1,2,4-trichlorobenzene); fGPC data in o-diehlorobenzene vs polystyrene standards

Figure 1. Optimized geometry for assumed catalytically-active species (ethylene coordinated species after 2M1P insertion, 2-methyl-2-butyl-heptyl). a) fert-BuCp analogue (2') and b) Cp* analogue (1'). Calculation: equilibrium geometry at ground state with semi-empirical PM3, geometry optimization, RHF/PM3D, Spartan Pro *04 for Windows (Wavefunction inc.). The results suggested that the Cp* analogue (1*) was more stabilized than ferf-BuCp analogue (2'), AE = 7.863 kcal/mol.

Figure 2 shows the optimized geometries for the proposed cationic alkyl species after a) 2M1P or b) ethylene insertion derived from 1. As assumed from our previous report [12], the agnostic interaction between titanium and P~

28. Ethylene/2-Methyl-l-pentene Copolymerization Catalyzed by Half-titanocenes 183

hydrogen was seen for the species after ethylene insertion (Figure 2b), and the calculated C-H bond distance (1,27 A) was somewhat longer than the ordinary values in the alkyl chain (ca. 1.11 A). In contrast, no distinct agnostic interactions were observed for the species after 2M1P insertion (Figure 2a), strongly suggesting that chain-transfer via hydrogen elimination by Ti should not be occurred after 2M1P insertion (with 1,2-insertion mode) in the copolymerization. Since the Mn values in the resultant copolymer prepared by 1 - MAO catalyst was not dependent upon the Al/Ti molar ratios, it is thus highly suggested that the dominant chain-transfer should not be the chain-transfer to the Al. Therefore, the dominant chain-transfer in the copolymerization should be p-hydrogen elimination after ethylene insertion and/or p-hydrogen elimination after 2M1P insertion with 2,1-insertion mode. The fact presented here was somewhat different from an assumption in the copolymerization of ethylene with isobutene using constrained geometry catalyst [3], and this may display another aspect as unique characteristics for using nonbridged halftitanocenes as catalyst precursors for precise olefin polymerization.

Figure 2, Optimized geometry for assumed eatalytically-active species (cationic alkyl species, Cp* analogue), a) after 2M1P insertion (2-methyl-2-butyl-heptyl) and b) after ethylene insertion (heptyl). Calculation: equilibrium geometry at ground state with semi-empirical PM3, geometry optimization, RHF/PM3D, Spartan Pro '04 for Windows (Wavefunction Inc.).

Acknowledgements This research is partly supported by The Sumitomo Foundation for Basic Science Research (051082). Authors express their thanks to Prof. Michiya Fujiki (NAIST) for helpful discussions, and express their thanks to Tosoh Finechem Co. for donating MAO (PMAO-S).

184

K. Nomura and K. Itagaki

References [I] H. H. Brintzinger, D. Fischer, R. Miilhaupt, B. Rieger, and R. M. Waymouth, Angew. Chem. Int. Ed. Engl. 34 (1995) 1143. [2] V. C, Gibson and S. K. Spitzmesser, Chem. Rev. 103 (2003) 283. [3] T. D. Shaffer, I A. M. Canieh, Macromolecules 31 (1998) 5145. [4] (a) H. Li, L. Li, T. J. Marks, L. Liable-Sands, A. L. Rheingold, J, Am. Chem. Soc. 125 (2003) 10788. (b) H. Li, L. Li, D. J. Schwartz, M. V. Metz, T. J. Marks, L. Liable-Sands, A. L. Rheingold, J. Am. Chem. Soc. 127 (2005) 14756. [5] W. Kaminsky, A. Bark, R. Spiehl, N. Moller-Linderhof, S. Niedoda, in: W. Kaminsky and H. Sirm (Eds.), Transition Metals and Organometallics as Catalysts for Olefin Polymerization, Springer-Verlag, Berlin, 1988, p. 291. [6] K. Nomura, K. Oya, Y. Imanishi, J. Mol. Catal. A 174 (2001) 127. [7] K. Nomura, H. Okumura, T. Komatsu, N. Naga, Macromolecules, 35 (2002) 5388. [8] K. Nomura, M. Tsubota, and M. Fujiki, Macromolecules 36 (2003) 3797. [9] W. Wang, M. Fujiki, and K. Nomura, J. Am. Chem. Soc. 127 (2005) 4582. [10] K. Nomura, K. Itagaki, M. Fujiki, Macromolecules 38 (2005) 2053. [II] K. Nomura, N. Naga, M. Miki, K. Yanagi, A. Imai, Organometallics 17 (1998)2152. [12] W. Wang, T. Tanaka, M. Tsubota, M. Fujiki, S, Yamanaka, K. Nomura, Adv. Synth. Catal. 347 (2005) 433.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

185

29 Synthesis and Optical Properties of Cycloolefin Copolymers Keun-byoung Yoon,H* Ho Young Lee,a Seok Kyun Noh,b Dong-ho Leea* "Department of Polymer Science, Kyungpook National University, Daegu 702-701, Korea School of Chemical Engineering and Technology, Yeongnam University, Gyeangsan 712-749, Korea

Abstract In ethylene/norbornene (E/NB) copolymerization, zPr(Cp)(Flu)ZrCl2 and SiMe2(Cp)2ZrCl2 catalysts exhibited more active than rac-Et(Ind)2ZrCl2 and SiMe2(Ind)2ZrCl2 catalysts. For ethylene/tetracyclododecene (E/TCD) copolymerization, the catalytic activity of rac-Et(Ind)2ZrCl2 was higher than that of iPr(Cp)(Flu)ZrCl2. Copolymers generated with rae-Et(lnd)2ZrCl2 contained NB microdiblocks with a maximum length of two NB units. The transmission of copolymers was above 90% over 300 ~ 900 nm. The refractive index(RI) of E/TCD copolymer was higher than that of E/NB eopolymer. The Rl of E/NB copolymer was found to be independent to NB contents, while, the Rl of E/TCD copolymer increased with increasing of TCD contents. 1. INTRODUCTION The modification of general purpose polyolefin materials to enhance their performance characteristics to the level of practical use as optical applications is currently a relevant topic for industrial as well as academic research. Cyclic olefin copolymers (COC) comprise one of the new classes of polymers based on cyclic olefin monomers and olefin [1]. Because of the bulky cyclic olefin units randomly or alternately attached to the polymer backbone, the COC becomes amorphous and shows the properties of high glass transition temperature, optical clarity, low shrinkage, low moisture absorption and low birefringence.

186

KB.Yoonetal.

With metallocene compounds of the new generation polymerization catalysts, Kaminsky discovered that cycloolefins of norbomene and its derivatives can be polymerized with keeping the cyclic structure of monomer itself [2]. By using the a«sa-metallocene compounds as catalyst and methylaluminoxane (MAO) cocatalyst, the cyclooefin can be copolymerized with olefin to obtain the COC. The effects of metallocene/MAO catalyst system and polymerization condition on the catalytic activity and composition of COC had been studied. The optical properties such as refractive index and UV-visible transmission of the obtained COC and commercial COC were also investigated, 2. EXPERIMENTAL Materials. The metallocenes such as SiMe2(Cp)2ZrCl2(Strem Chem., U.S.A.), rae-Et(Ind)2ZrCl2 (Stem Chem., U.S.A.), SiMe2(Ind)2ZrCl2(Strem Chem., U.S.A.) and ?Pr(Cp)(Flu)ZrCl2 (Boulder Sci., U.S.A.) were purchased and used as received. Modified methylaluminoxane (MMAO, Type-4, 6.4 wt% Al, Akzo, U.S.A) was used without further purification. The cycloolefins such as norbomenefNB) and tertracyclododecene(TCD) were purchased and used after drying and purification. Preparation, In glass reactor were introduced sequentially the proper amounts of toluene, cycloolefins and MMAO solutions and then the system was saturated with ethylene(E). With a continuous flow of E, the polymerization was initiated by injecting toluene solution of metallocene. Characterization. The composition of the produced polymer was analyzed with 13 C-NMR (Varian, Unity, 400MHz). The glass transition temperature (Tg) was estimated with DSC. The transmission of UV-visible light for polymer film was measured with UV-Visible Spectroscopy (Shimadzu/UV-1201). The refractive index(RI) of the polymer product was measured with prism coupler (Matricon 2010). 3. RESULTS AND DISCUSSION The copolymerization of E and cycloolefins such as NB and TCD were conducted with metallocenes such as iPr(Cp)(Flu)ZrCl2 , SiMeafCp^ZrClj, racEt(Ind)2ZrCl2 and SiMe2(Ind)2ZrCl2 with MMAO cocatalyst, and the experimental results are shown in Table 1 and 2. In the E/NB copolymerization, the catalytic activity of iPr(Cp)(Flu)ZrCl2 and SiMe2(Cp)2ZrCl2 exhibited higher than that of rac-Et(Ind)2ZrCl2 and SiMe2(Ind)2ZrCl2 due to the lager angle and lower steric hindrance of catalyst geometry (Ligand-Zr-Ligand). On the other hand, the catalytic activity of raeEt(Ind)2ZrCl2 was higher than that of iPr(Cp)(Flu)ZrCl2 for E/TCD copolymerization.

29, Synthesis and Optical Properties afCycloolefin Copolymers

187

Table 1. Copolymenzation of Ethylene andNorbomene with Various Metallocenes Feed (mol/L) N B contents Activity a) Tg(°C) (mol%) b) [E]/INB] 42 0.01/0.1 3057 138 iPr(Cp)(Flu)ZrCl2 52 0.01/0.2 2334 179 133 46 0.01/0.1 675 rac-Et(Ind)aZrCl2 52 0.01/0.2 525 167 132 42 0.01/0.1 1814 SiMe2(Cp)2ZrCl2 47 0.01/0.2 1820 173 43 0.01/0.1 931 138 SiMe2(Ind)2ZrCl2 51 0.01/0.2 360 175 Polymerization conditions : [Zr]= 3.5 x 10"s mol/L, [Al]/[Zr]=3000,40 °C, latm, lh a)Activity : kg-polymer/mol Zrhratm , b) Characterized by C-NMR Catalysts

Table 2. Copolymenzation of Ethylene and Tetracyclododecene with Various Metallocenes Catalysts iPr(Cp)(Flu)ZrCl2 SiM62(Cp)2ZrCl2 rac-EtCIndJjZrCfe

Feed (mol/L) [E]/[TCD] 0.002/0.006 0.002/0.012 0.002/0.006 0.002/0.012 0.002/0.006

Activity"'

TgfC)

205 157 337 169 965

103 140 122 173

TCD contents (mol%) b) 15 32 e) 39C)

65

9

Polymerization conditions : [Zr]= 2.5 x 1 0 3 mol/L, [Al]/[Zr]=3000, 40 "C, latm, l h a) Activity : kg-polymer/mol Z r h r a t m , b) Characterized by 13 C-NMR, c) Calibration curve from J.Y. S h i n e t a l . [3]

The Tg of E/NB copolymer increased up to 179 °C and that of E/TCD copolymers dramatically increased with small incorporation of TCD in copolymer. The variation of Tg with cyclic monomer content for the TCD was bigger that that of the NB, which implies that the polycyclic unit TCD, which has bulkier structure of the bicyclic NB unit, led to a restricted local motion of chain segments [3]. The microstructures of copolymers were investigated with 13C-NMR and the results are shown in Figure 1. (a)

r

-i

(b)

Figure 1. 1 3 C-NMR spectra of E/NB copolymers obtained with (a) !Pr(Cp)(Flu)ZrCl 2 and (b) racEt(Ind) 2 ZrCl 2

188

KB. Yoon et al.

The copolymers generated with rac-Et(md)2ZrCI2 contained NB microdiblocks with a maximum length of two NB units while iPr(Cp)(Flu)ZrCl2 gave a mainly alternating copolymer with trace amounts of NB microdiblocks [4]. The total light transmission of copolymers was above 90% over 300 - 900 rim from UV-visible spectra. The transmission of E/NB copolymer was higher than that of E/TCD at lower wavelength (below 300 nm). The RI of COC film had been investigated with the variation of polymer composition, and the results are shown in Figure 2.

0 a Commercial

15100

l

m

30 a> N B muJTCD Contents ( n o l « . )

in

Figure 2. Refractive Index of copolymers at various copolymer compositions

The RI of E/TCD copolymer was higher than that of E/NB copolymer. The RI of E/NB copolymer less changed with NB contents, while, the RI of E/TCD copolymer increased with increasing of TCD contents. The thermo-optic coefficient (TOC) was calculated from RI of copolymers at various temperatures[5], and that was found that TOC values (~ 3.0 x 10"5/°C) of COC were lower than other amorphous polymers. References [1] G. Khanarian, Opt. Engineer., 40 (2001) 1024. [2] D.H. Lee, Y.Y. Choi, J.H. Lee, Y.S. Park, and S.S. Woo, e-Polymers, (2001) no. 019. [3] J.Y. Shin, J.Y. Park, C. Liu, J. He, S.C. Kim, Pure Appl. Chem., 77 (2005) 801. [4] I. Tritto, L. Boggioni, M.C. Sacchi, P. locatelli, D.R. Ferro, A. Provasoli, Macromol. Rapid Commun., 20 (1999) 279. [5] Y.L. Lo, C.P. Kuo, IEEE Trans. Adv. Packag., 25 (2002) 50.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

189

30

Effects of Temperature in Syndiospecific Living Polymerization of Propylene with [^-BuNSiMe2(3,6*-Bu2Flu)]TiMe2-MMAO Catalyst Zhengguo Cai, Nakayama Yuushou, Takeshi SMono* Graduate School of Engineering, Hiroshima University, Kagamiyama I-4-l, HigashiHiroshima 739-8527, Japan

Abstract Propylene polymerizations were conducted by [/-BuNSiMe2(3,6~£Bu2Flu)]TiMea using trialkylaluminum-free modified niethylaluminoxane as a cocatalyst in toluene at -20, 0 and 25 °C. The raise of polymerization temperature improved the activity to produce 2400 kg of polymer per mole of Ti per hour at 25 °C, and the post-polymerization testified that the propylene polymerization proceeded in a living manner regardless of the polymerization temperature. The polymerization temperature also influenced the stereoregularity of the polypropylenes (PP). The system gave syndiotactic crystalline PP at -20 °C with a melting point of 129 °C and amorphous PP at 25 °C, respectively. 1. INTRODUCTION Single-site catalysts based on group 4 metallocene complexes have been investigated for the development of new olefin polymerization catalysis [1,2]. Intense effort has been paid to elucidate the effects of polymerization conditions (cocatalyst, monomer concentration, solvent, temperature, etc.) on the polymerization behaviour. Polymerization temperature is one of the most important factors that largely influence the activity and the stereospecificity. We have previously reported that [r-BuNSiMe2(3,6-£-Bu2Flu)]TiMe2 (1) activated by trialkylaluminum-free modified methylaluminoxane (dMMAO) conducted highly syndiospecific living polymerization of propylene in heptane at 0 °C[3].

190

Z.Caietal

In the present work, we investigated the effects of polymerization temperature on the syndiospecificity of the present catalyst in toluene. 2. EXPERIMENTAL Materials. All operations were performed under argon gas using standard Schlenk techniques and all solvents were dried by usual procedures and freshly distilled before use. The complex 1 and dMMAO were prepared according to the procedures reported previously[3,4]. Research grade propylene (Takachiho Chemicals Co.) was purified by passing it through columns of NaOH, PaOj, and molecular sieves 3 A, followed by bubbling it through a NaAlH2Et2/l,2,3,4,tetrahydronaphthalene solution. Polymerization Procedure. Polymerization was performed in a 100 mL glass reactor equipped with a magnetic stirrer and carried out by the following methods. After a certain amount of dMMAO solution in toluene had been saturated with an atmospheric pressure of propylene, polymerization was started by the addition of 1 mL solution of 1. Polymerization was conducted for a certain time and terminated with acidic methanol. The polymers obtained were adequately washed with methanol and dried under vacuum at 60 °C for 6 h. Analytical Procedures. Molecular weight and molecular weight distribution of polymer obtained were determined by gel permeation chromatography with a Waters 150 CV at 140 °C using o-dichlorobenzene as a solvent. The parameters for universal calibration were K = 7.36 x 10"s, a- 0.75 for polystyrene standard and K = 1.03 x 10"4, cr = 0.78 for PP samples. The 13C NMR spectra of PPs were measured at 130 °C on a JEOL JNM-400 spectrometer operated at 400 MHz in the pulse Fourier-Transform mode. The pulse angle was 45° and about 10 000 scans were accumulated in pulse repetition of 5.0 s. Sample solutions were prepared in I,l,2,2-tetrachloroethane-d2 and the central peak of the solvent (74.47 ppm) was used as an internal reference. Differential scanning calorimetry (DSC) analyses were performed on a Seiko DSC-220 and the DSC curves of the samples were recorded under a nitrogen atmosphere with a heating rate of 10 °C/min from 20-200 °C. 3. RESULTS AND DISCUSSION 3,1. Propylene polymerization at various temperatures Propylene polymerizations were conducted with 1-dMMAO in toluene at -20 °C, 0 and 25 °C by a semi-batch method. Polymerization was quenched before the produced polymer would interrupt effective stirring according to the

JO. Effects of Temperature on Living Polymerization ofPropylene

191

polymerization temperature. The results are summarized in Table 1. The catalytic system gave the polymers with comparatively narrow molecularweight distribution (MWD) regardless of the polymerization temperatures. The raise of polymerization temperature enhanced the activity but did not affect the number of polymer chains (N), which was about 60 - 65 % of the Ti used. These results suggest that the catalytic system should conduct living polymerization of propylene. To investigate the living nature of 1-dMMAO at these temperatures, we conducted post-polymerization by a batch method. The results of the post-polymerization indicate that the propylene polymerization proceeded in a living manner in toluene at -20, 0 and 25 °C. Table 1 Results ofPropylene Polymerization with 1-dMMAO entry

temp.

time

yield

activity h

Mnc

MJMn* 4

(xlO )

Nd

rf

T

r

fC)

(°C)

(min)

(g)

1

-20

8

0.76

285

6.5

1.35

12

0.90

129

2

0

4

2.36

1768

18.8

1.36

13

0.83

100

3

20

3

2.42

2420

17.9

1.32

13

0.60

Qimol)

a

Polymerization conditions: toluene = 30 mL, Ti = 20 junol, Al = 4.0 mmol, propylene =1,0 atm. Activity in kg-PP/(mol~Ti»h). c Number average molecular weight and molecular weight distribution determined by GPC using universal calibration. d Calculated from yield and Mn. e Determined by I3C NMR. f Melting temperature determined by DSC. BNot detected.

b

3.2. Structures of Polypropylene® obtained at various temperatures The steric pentad distributions were determined from the resonances of methyl carbons in 13C NMR spectra, and the results are shown in Table 2. The PP obtained at -20 °C showed the highest syndiotactic pentad value (rrrr) of 0,90, which decreased according to the raise of polymerization temperature to 0.83 at 0 °C and 0.60 at 25 °C. Consequently the PP obtained at -20 °C was crystalline polymer with melting point of 129 °C, whereas that obtained at 25 °C was amorphous one. In the enantiomorphic-site controlled syndiospecific polymerization with a Cs symmetric catalyst, two types of stereodefects should be formed: one is "rmrr" arising from the "chain migration" without monomer insertion and the other is "rmmr" arising from the "monomer miss-insertion" [5]. Table 2 indicates that rmrr content was increased by the raising polymerization temperature, -20 °C (0.02) < 0 °C (0.10) < 25 °C (0.23), whereas the rmmr content was almost constant and slightly increased only at 25 °C, -20 °C (0.02) = 0 °C (0.02) < 25 °C (0.04). These results imply that the decrease of the syndiospecificity caused

192

ZCaietal

by raising the temperature is mainly attributed to the frequent "chain migration". The similar phenomena were observed in the syndiospecific propylene polymerization with Cs-symmetric zirconocene catalysts[6-8]. Table 2 Stene Pentad Distributions of Polypropylenes Obtained at Various Temperatures Steric pentad content

entry (temp)

mmmfli

mmmr

rmmr

mnirr

TO

rmrr +

nnrni

rrrr

mrrr

mrrm

mmrm

1 (-20)

0.00

0.00

0.02

0.05

0.02

0.01

0.83

0,07

0.00

2(0)

0.00

0.00

0.02

0.04

0.10

0.01

0.70

0.13

0.00

3(25)

0.00

0.01

0.04

0.09

0.23

0.06

0.39

0.20

0.01

"Determined by 13C NMR.

4. CONCLUSIONS The effects of polymerization temperature were investigated in propylene polymerization by 1-dMMAO in toluene under an atmospheric pressure of propylene. The activity increased by raising the temperature from -20 °C to 25 °C with keeping living polymerization accompanied by the decrease of the syndiospecifieity. The system gave syndiotactic crystalline PP with a melting point of 129 °C at -20 °C and amorphous PP at 25 °C. Acknowledgements This work was supported by the New Energy and Development Organization (NEDO) for the Project on Nanostructured Polymeric Materials. We thank Tosoh-Finechem Co. for donating MAO. References [1] W. Kaminsky, Advances in Catalysis 46 (2001) S9-159. [2] V. C. Gibson, S. K. Spitzmesser, Chem. Rev. 103 (2003) 283-315. [3] Z. Cai, T. Ikeda, M. Akita, T. Shiono, Macromolecules 38 (2005) 8135-8139. [4] H. Hagimoto, T. Shiono, T. Ikeda, Macromol. Rapid. Common. 23 (2002) 73-76. [5] J. A. Ewen, M. J. Elder, R. L. Jones, L. Haspeslagh, J. L. Atwood, S. G. Bott, and K. Robinson, Makromol, Chem., Macromol. Symp. 48/49 (1991) 253-295. [6] J. A. Ewen, M. J. Elder, R. L. Jones, S. Curtis, H. N. Cheng, Stud. Surf. Sci. Caial. 56 (1990) 439-412. [7] D. Veghini, L. M. Henling, T. J. Burkhardt, J. E. Bercaw, J. Am. Chem. Soc. 121 (1999) 564573. [8] M.-C. Chen, T. J. Marks, J. Am. Chem. Soc. 123 (2001) 11803-11804.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

193 193

31 Copolymerteation of Styrene Derivatives and Cycloolefin with Ni Compound/MAO Catalyst Naoya Nishimura, Katsuya Maeyama, Akinori Toyota* Graduate School of Engineering, Tokyo University of Agriculture and Technology, 224-16 Naka-eho, Koganei-shi, Tokyo 184-8588, Japan, email: [email protected],ac,jp

Abstract Copolymerization of styrene derivatives, such as 4-tert-hutylstymne (4TBS), 4-methylstyrene (4MS), 4-methoxystyrene (4MOS), 4-bromostyrene (4BS), and 5-ethylidene-2-norbomene (ENB) was conducted with nickel (Ni) compound/methylaluminoxane (MAO) catalysts. Polymerization behaviors and properties of the resulting copolymers were investigated. Nickel bis(acetylacetonate) (1) / MAO showed the highest activity. Ts values of the obtained copolymers reached to ca. 300 °C. 1. INTRODUCTION Recently, papers related to copolymerization of cycloolefin and olefms have been reported[l,2], Cycloolefin copolymers have been attractive because they have the excellent properties such as high glass transition temperature, high optical transparency, low birefringence, and low moisture absorption. Copolymerization of cycloolefin with styrene has also been investigated because it is easy to obtain copolymers with higher glass transition temperature than the copolymers derived from cycloolefin/olefin. However few reports have been known on copolymerization of cycloolefin with styrene derivatives[3,4]. In this paper, we would like to report the studies on the effects of the catalyst structure and those of polymerization conditions on the activities and copolymerizability in the copolymerization with Ni compound/MAO catalysts.

194

JV. Nishimura et al.

2. EXPERIMENTAL All procedures were conducted with using Schlenk techniques under nitrogen atmosphere. Styrene derivative and ENB were placed in a 50-ml flask, and then a nickel compound (2.5 X 10"6 mol) and MAO (2.5 X 10"3 mol) were sequentially charged into the flask. The reactions were carried out at room temperature for 24 h. After completion of the reaction, excess methanol was added. The resulting polymers were purified by reprecipitation with a system of CHCls/methanol and the polymer precipitates were dried in vacuum.

CH 3

CH 3

Ni(acac)2 1

Ni stearats

bis(3,5-di-terf-butylsalicylidene}1,2-cyclohexadiamino nickel 2 3 Figure 1 Ni compounds used for copolymerization

3. RESULTS AND DISCUSSION Results of 4TBS-ENB copolymerization are shown in Table 1. 4TBSENB copolymers were obtained with all nickel compound/MAO catalysts. M(acac)2 (1) /MAO catalyst showed the highest activity among the three types of nickel compounds. ENB contents increased with increasing ENB in feed. ENB contents in copolymers were in the range from 1 4 - 5 5 mol %. This is probably due to bulkiness of 4TBS. Number average molecular weight was low, and polydispersiry was narrow. The Tg values of copolymers increased with increasing ENB content in the copolymer and reached to ca. 300 °C. Relation of between Te and ENB content in the copolymer is shown in Figure 2.

31. Copolymerization ofStyrene Derivatives and Cycloolefin with Ni compdJMAO 195 Table 1 Copolymerization of 4TBS and ENB with Ni compound/MAO catalyst* ENB in feed

ENB content0

b

entry

catalyst

1

1

10

2.38

33.8

3.9

2.8

189

2

1

30

1.94

39.0

3.6

1.6

200

3

1

50

3.54

47.6

4.1

1.8

218

4

1

70

1.47

53.4

3.8

1.8

227

5

2

10

1.00

24.8

4.7

1.4

169

6

2

30

0.870

34.6

4.4

1.6

220

7

2

50

1.09

47.1

4.4

1.5

234

8

2

70

0J36

52.4

4.2

1.6

296

9

3

10

0.976

14.6

3.3

1.3

164

10

3

30

2.39

29.8

4.3

1.7

176

11

3

50

2.61

35.5

4.5

1.8

196

12

3

70

1.86

55.8

4.1

1.8

244

Activity

(xlO3)

TO

"Polymerization conditions: total volume = 25 mL, solvent = toluene, Ni = 2.5 ^mol, Al /Ni= 1000, temperature = r.t., time = 24 h. hactivity = kg (p^) mol ^'l h"1, "determined by 'H-NMR, number average molecular weight and molecular weight distribution were determined by GPC using polystyrene standards, 'determined by DSC. 350 350 300 300 -250 250

Tg [oC]

Copolymerization of 4MS and ENB with three types of Ni/MAQ catalysts afforded copolymers. Copolymerization of 4BS and 4MOS with ENB was investigated with using Ni (1)/MAO catalyst. Correlations between Tg and ENB content are shown in Figures 3 and 4. On the other hand, 4MOS homopolymer was obtained in copolymerization of 4MOS and ENB. This polymerization probably proceeds via cationie polymerization predominantly.

8°'

D

200 150 150 100 -_ 100

O

Ni(acac)2

1 l Ni stearate Ni (salen)

50 50 0

10 10

20 20

30 30

40 40

50 50

ENB content [mol%]

Figure 2 Fg vs. ENB content for poly (4TBS-co-ENB)

60

196

N. Nishimura et al. 350 350

350

300 300

300 -

.

2000 20

o

„ 250 O

Tg [oC]

Tg [oC]

2500 25

o

f-M 200 -

150 150 100 - °CP 100

o n

A

50

00

10 10

20 20

30 30

050 150

Ni(acac)22 Ni stearate Ni (salen)

40 40

50 50

ENB content [mol %] %] Figure 3 Tg vs. ENB content for poly (4MS-CO-ENB)

< 60 60

100 inn

00

4BS-ENB

10 10

20 20 30 30 40 40 50 ENB content [mol %] %]

60

Figure 4 Tg vs. ENB content for poly (4BS-CO-ENB) obtained with Ni(acac)2 /MAO catalyst

4BS-ENB copolymers were obtained with Ni(acac)2/MAO catalyst. The Tg values of copolymers ranged from 120 to 220 °C. These copolymers have possibilities to be modified at bromo group and to be converted to functional polymers. 4. CONCLUSIONS Copolymerization of styrene derivatives and ENB was studied with using three types of nickel compounds-MAO catalysts. The catalysts showed low activity for the copolymerization, but copolymers having high Tg values in range of 90 to 300 °C were obtained. References [1] T. Hasan, T. Ikeda, and T. Shiono, Macromolecules 38 (2005) 1071-1074. [2] J. Forsyth, J. M. Perena, R. Benavente, E. Perez, 1 Tritto, L. Bogginoni, and H. H. Brintzinger, Macromol. Chem. Phys. 202 (2001) 614-620. [3] H. Suzuki, S. Matsumura, Y. Satoh, K. Sogoh, and H. Yasuda, React. Fund Polym, 58(2004)77-91. [4] C. Zhao, M.R. Ribeiro, M. F. Portela, S. Pereira, and T, Nunes, Eur, Patym. J. 37(2001)45-54.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

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32

Additive Effects of Dialkylaluminum Hydrides on Propylene~l,3-Butadiene Copolymerization Using an Isospecific Zirconocene Catalyst Takeshi Ishihara,a Hoang The Ban,a Hideaki Hagihara,b Takeshi Shionoc a

Japan Chemical Innovation Institute, AIST Tsukuba, Central 5-8, 1-1-1 Higashi, Tsukuba, Iharaki 305-8565, Japan b National Institute of Advanced Industrial Science and Technology, Tsukuba, Central 5-8, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8565, Japan e Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, Higashi-Hiroshima 739-8527, Japan

Abstract Additive effects of dialkylaluminum hydrides on propylene-l,3-butadiene copolymerization were investigated with an isospecific zirconocene catalyst, rac-dimethylsilylbis(2-methyl-4-phenylindenyl)zirconium dichloride (4Ph), activated by modified methylaluminoxane. Dialkylaluminum hydrides improved the apparent selectivity for 1,2-insertion of 1,3-butadiene to give a pendant vinyl group. 13C NMR analysis of the eopolymers indicated that the dialkylaluminum hydride converted the 1,4-inserted butadiene unit in the copolymer to tetramethylene unit after methanolysis. 1. INTRODUCTION Polypropylene (PP) has been expanding its usage due to its mechanical balance and economical advantage. PP is, however, so hydrophobic that many attempts have been made to improve affinity of PP with other polar materials [1-2]. We have been developing copolymerization techniques to control the amount and location of polar groups in PP chain and succeeded in the selective introduction of carbon-carbon double bond as a precursor of polar group by the copolymerization of propylene and 1,3-butadiene using isospecific zirconocene

198

T. Ishihara et al,

catalysts [3-4]. The addition of hydrogen was found to hydrogenise the 1,4inserted butadiene units (1,4-BD) in the copolymer, and selectively produced PP with pendant vinyl groups. In this paper, therefore, we investigated the additive effects of dialkylaluminum hydrides on the copolymerization whether the dialkylaluminum hydrides react with 1,4-BD to produce PP having dialkylaluminum group on the main chain of the copolymer or not. 2. EXPERIMENTAL Materials. 4Ph commercially obtained from Boulder Scientific Company, and modified methylaluminoxane (MMAO) and other aluminum compounds purchased from Tosoh-Finechem. Co., were used without further purification. Other chemicals commercially obtained were purified according to the usual procedures. Polymerization procedure, Copolymerization of propylene with 1,3-butadiene was conducted in a 100-mL stainless steel autoclave by batch-wise operation at 0°C. Analytical procedures, 'H TSTMR and I3C TSTMR spectra were obtained in 1,1,2,2tetrachloroethane-d2 at 120 °C on a JEOL JNM-LA600 spectrometer. Molecular weights and molecular weight distributions of the copolymers were determined by a PL-GPC210 at 140 °C using o-dichlorobenzene as a solvent. 3. RESULTS AND DISCUSSION 3.1. Results of copolymerization The results of propylene-l,3-butadiene copolymerization using 4Ph-MMAO system are summarized in Table 1.

the

Table 1. Additive effects of aluminum compounds on propylene— 1,3-butadiene copolymerization*

additive

Yield (B)

Rsp (kgpolymer / mol-Zr»h) 13.1 15.8 35.8

(xlO3)

MJ Mnb

Mole fraction6 (%) 1,21,4H-1,4 BD BD -BD 1.43 0.76 0 0.23 1.26 0.63 0.26 0.4S 1.59

Selectivity {%) i *} nn

nan 0.08 2.4 65.3 35.7 84.6 0.1 34.2 DEAL-H 1.6 0.21 85.9 3.9 13.0 DiBAL-H "Polymerization conditions: solvent (toluene) = 40 mL, 4Ph = 2 jimol, MMAO = 4.0 mmol, 0 °C, 3 h, propylene concentration 1.8 mol / L, butadiene concentration 90 mmol / L. bNumber average molecular weight and molecular weight distribution determined by GPC using universal calibration.e Calculated from 'H and 13C NMR spectra. A Selectivities were the relative ratios of 1, 2—BD mole fractions to all double bonds.

32. Additive Effects ofDiatkylatuminum Hydrides

199

Dialkylaluminum hydrides, i.e., diethylaluminum hydride (DEAL-H) and diisobutylaluminum hydride (DiBAL—H), increased polymerization activities. The addition of DEAL-H did not affect the molecular weight (Mn) of the copolymer, whereas the introduction of DiBAL—H decreased the Ma value. An increase in polymerization activity accompanied by a decrease of molecular weight indicates that DiBAL-H caused chain transfer reaction. 3.2. Structures of copolymers The addition of the dialkylaluminum hydrides caused the decrease of 1,4—BD in the copolymer as observed in the *H NMR spectra (Fig. 1). The selectivity for 1, 2-BD in copolymers determined by 'H NMR are shown in Table 1.

I III-AI -II

Fig.l H NMR spectra of propylene- 1, 3- butadiene capolymer with and without DiBAL-H

[I'M

Fig, 2 " C NMR spectra of propylene-1, 3butadiene eopolymers synthesized with and without DiBAL-H.

The selectivity was improved from 65 to 85 % by the addition of the dialkylaluminum hydrides. To investigate the structures of copolymers in more details, we measured the 13C NMR spectra of copolymers obtained with and without DiBAL-H (Fig. 2). The signals assignable to pendant vinyl group and those to 1,4-BD structure were observed in both samples. The addition of DiBAL-H, however, caused the emergence of new signals derived from hydrogenated 1,4-BD (H-1,4-BD). The total mole fractions of 1,4-BD and H-1,4-BD were unchanged by the addition of the dialkylaluminum hydrides

200

T. Ishihara ct al.

(Table 1). The results indicate that the dialkylaluminum hydrides did not affect the mode of butadiene insertion but hydroaluminated the 1,4-BD units. A plausible copolymerization mechanism is shown in Scheme 1. Dialkylaluminum hydride and propylene competitively react with 7t-allyl Zr complex formed by 1,4-insertion of butadiene (A in Scheme 1). Insertion of propylene to A forms 1,4-BD in main chain (C), When dialkylalunium hydride reacts with A, hydroaluminated 1,4-BD is formed (B, D), which could incorporate successive propylene insertion more smoothly. The hydroaluminated 1,4-BD gives H—1,4—BD in main chain after methanolysis (E). Scheme 1 Reaction scheme &rpropylene-l,3-butadiene copolymerization with zirconocene— MMAO-dialkylaluminum hydride

4. CONCLUSIONS The 4Ph-MMAO-dialkylaluminum hydride system produced PP copolymer with pendant vinyl group. Although their selectivity of reduction from 1,4-BD to H—1,4—BD was lower than that with hydrogen [4], the copolymer possessed dialkylaluminum groups in main chain which can be utilized for functionalization of PP. Acknowledgements This work was supported by the New Energy and Development Organization (NEDO) through a grant for "Project on Nanostructured Polymeric Materials" under the Nanotechnology Program. References [1] T. C. Chung, Prog. Polym. Sci. 27 (2002) 39-85. [2] G. Moad, Prog. Polym. Sci. 24 (1999) 81-142. [3] T. Ishihara and T. Shiono, Macromolecules 36 (2003) 9675-9677. [4] T. Ishihara and T. Shiono, J. Am. Chem. Soc. 127 (2005) 5774-5775.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

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33

Pd Complex-Promoted Cyclopolymerization of Diallylmalonates Sehoon Park, Daisuke Takeuchi, Kohtaro Osakada* Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Yokohama, 226-8503, Japan

Abstract Pd complexes prepared in situ from PdCl(Me)(diimine) and NaBARF (BARF = [B{CgH3(CF3)2-3,5}4]') initiate cyclopolymerization of isopropylidene diallylmalonate (I) in CH2CI2 to produce poly-I containing tmn$-\,2disubstituted cyclopentane groups. 1. INTRODUCTION The cyclopolymerization of nonconjugated dienes converts acyclic monomers into polymers with cyclic repeating units. The complexes of the early transition metals Ti, Zr, and Y catalyze the polymerization of 1,5-hexadiene and 1,6heptadiene to produce polymers with 1,3-disubstituted five- and six-membered cyclic repeating units.1 These polymers, however, consist of both trans- and eis-fused rings arranged randomly in a polymer chain. Stereoseleetive cyclopolymerization is of importance because polymers whose cyclic repeating units are arranged in a controlled manner exhibit unique properties such as a high Fm and a high Tg.2 The complexes of late transition metals such as Ru, Rh, and Pd have recently been reported to catalyze the cyclization of enynes and dienes.3'4 The Pd catalyst [PdCl(Me)(phen)]-NaBARF (BARF = [B{C6H3(CF3)2~3,5}4]~ catalyzes the cyclizative hydrosilylation and cycloisomerization of diallylmalonates to afford compounds with 1,2disubstituted trans-fused five-membered rings.5 The combination of the stereoselective ring formation and the insertion of a C=C bond of a diene, which occur alternately, produces the polymers with cyclic repeating units with a high

202

S. Park et al

regularity. In this paper, we report the Pd complex-catalyzed cyclopolymerization of diallyl malorates to produce polymers with fivemembered rings. A part of results were reported in a preliminary form.6 2. RESULTS AND DISCUSSION Pd complexes for the polymerization have been prepared in situ by addition of NaBARF (BARF = [B{C5H3(CF3)2-3,5}4]") to a CH2C12 solution of PdCl(Me)(diimme).7 Addition of isopropylidene diallylmalonate (I) to a solution of the catalyst prepared from la-NaBARF initiates cyclization polymerization of the diene to produce polymer -(CHj-CsHgfCsHgO^-CHaJn(poly-I) (eq. 1). The 'H NMR spectrum of poly-I, shown in Figure 1, indicates

1a: R1 = R2 = 'Pr, R3 = H 1b: R1 = R2 = R3 = Me

EtOOC

COOEt

+NaBARF CHaGI2 r.t.

Chart 1 poly-I

that the polymer consists of the repeating units with the five-membered ring. The ( H NMR signal at 3 1.95 (A) and the "C-^H} NMR signal at n 345.E are attributed to the CH2 d,e .0 group of the cyclopentane groups, while the CH group °^> f gives rise to 'H and 13C{'H} . 1 NMR signals at S 2.46 and S /- : 46.6-47.1, respectively. Sharp a e 4 2 os shape of the CH2 carbons of Figure 1. 1H NMR spectrum of poly-I in CDCI3 at 25 . Poly-I was prepared by polymerization of I in CHgClj under cyclopentane group and main Ar catalyzed by 1a/NaBARF ([Pd] = 10 mM, [la]/[Pd] = 70} chain indicates regulated at room temperature. The peaks with an asterisk are due stereochemistry of the produced to solvent. polymer. The JH NMR spectrum did not show signals in the region of vinyl hydrogens. CH carbon signals of the trans- and eis-cyelopentane-l,2-diyl group in the polymer obtained by the copolymenzation of 1,3-butadiene and ethylene are 8 46.5 and 43.2, respectively.8 The chemical shift of the CH carbon signal of poly-I (^46.6-47.1) is close to the trans repeating unit rather

33. Pd Complex-Promoted Cyclopofymerization of Dialfylmalonates

203

than cis repeating unit. This result indicates that the 1,2-disubstituted cyclopentane ring of the produced polymer adopts trans configuration quantitatively. The molecular weight of the polymer obtained by l a ([I]/[la] = 70) is estimated by GPC (polystyrene standard) to be Mn = 7900 (MJMn =1.51) (Table 1, run 1). Table 1 Polymerization of Diallyl Monomers by Pd Complexes" ran

monomer

Pd

solvent

time

conv.

(mL)

Mn

MJMn

(h)

(%)

1

I

la

0.5

48

80

8500

1.60

2

I

1b

0.5

12

82

9000

1.66

3

II

lb

0.25

24

22

5800

1.43

4

III

la

0.5

12

40

3600

1.28

5

1,6-heptadiene

lb

0.25

72

trace

-

-

6

diallyl ether

lb

0.25

72

trace

-

-

Reaction Conditions: Pd complex = 0.01 mmol, NaBARF = 0.012 mmol, [monomer]/[Pd] = 70, solvent = CHZC12, at r.t.

The Pd-catalyzed cyclization polymerization is applicable to other monomers listed in Chart 1 (Table 1). Diethyl diallylmalonate II, which does not have cyclic structure, also undergoes cyclization polymerization somewhat slowly to give the polymer having cyclopentane structure (run 3). Ill, which does not have carbonyl group, also polymerizes, although the polymerization get slower around 50% conversion (run 4), These results indicate that the cyclic structure and carbonyl group of the isopropylidene diallylmalonate are important for the smooth polymerization. On the other hand, 1,6-heptadiene and diallyl ether, which have no substituents between two vinyl groups of the monomers, do not give polymer (runs 5,6). These monomers with acyclic structures and without carbonyl groups do not produce high mass polymer because of chain walking of the Pd center during the reaction. Acknowledgements This work was supported by a Grant-in-Aid for Young Scientist No. 16750091 for Scientific Research from the Ministry of Education, Science, Sports and Culture, Japan.

204

S.Parketal.

References [1] (a) Y. Doi, N. Tokuhiro, K. Soga, Makromol. Chem. 190 (1989) 643. (b) L. Reseoni, R. M. Waymouth, J. Am. Chem. Soc. 112 (1990) 4953. (c) G. W. Coates, R. M. Waymouth, J. Am, Chem. Soc. 113 (1991) 6270. (d) M. R. Kesti, G. W. Coates, R. M. Waymouth, J. Am. Chem. Soc. 114 (1992) 9679. (e) C, J. Schaverien, Organometallics 13 (1994) 69. (f) M. Mitani, K. Oouchi, M. Hayakawa, T. Yamada, T. Mukaiyama, Chem. Lett. (1995) 905. (g) N. Naga, T. Shiono, T. Ikeda, Macromol. Chem. Phys. 200 (1999) 1466. (h) K. C. Jayarantne, R. J. Keaton, D. A. Henningsen, L. R. Sita, J. Am. Chem. Soc. 122 (2000) 10490. (i) P. D. Hustad, J. Tian, G. W. Coates, J. Am. Chem. Soc. 124 (2002) 3614. [2] (a) C. Janiak, P. G. Lassahn, Macromol. Rapid Commun. 22 (2001) 479. (b) I. Natori, K. Imaizumi, H. Yamaguehi, M. Kazunori, J. Polym. Sci. Part B. Polym, Phys. 36 (1998) 1657. [3] Reviews on cycloisomerization of dienes and enynes: (a) B. M. Trost, M. J. Krisehe, Synlett. (1998) 1. (b) G. C. Lloyd-Jones, Org. Bio. Chem. 1 (2003) 215. [4] Pd-catalyzed cycloisomerization of dienes: (a) R. Grigg, T. R. B. Mitchell, A. Ramasubbu, J, Chem. Soc. Chem. Commun. (1979) 669. (b) R. Grigg, J. F. Malone, T. R. B. Mitchell, A. Ramasubbu, R. M. Scott, J. Chem. Soc. Perkin Trans, 1 (1984) 1745. (c) B. Radetich, T. V, RajanBabu, J. Am. Chem. Soc. 120 (1998) 8007. (d) A. Heumann, M. Moukhliss, Sylnett (1998)1211. (e) K. L, Bray, I. J. S. Fairlamb, G, C. Lloyd-Jones, Chem. Commun. (2001) 187. (f) K. L. Bray, J. P. J. Charmant, I. J. S. Fairlamb, G. C. Lloyd-Jones, Chem. Eur. J. 7 (2001) 4205. (g) K. L. Bray, I. J. S. Fairlamb, J.-P. Kaiser, G. C. Lloyd-Jones, P. A. Slatford, Top. Cat. 19 (2002) 49. (h) A. Heumann, L. Giordano, A. Tenaglia, Tetrahedron Lett. 44 (2003) 1515. (i) A. Cortna, H. Garcia, A. Leyva, J. Organomet. Chem. 690 (2005)2249. [5] (a) R. A. Widenhoefer, M. A. DeCarli, J. Am. Chem. Soc. 120 (1998) 3805. (b) N. S. Perch, P. Kisanga, R. A. Widenhoefer, Organometallics 19 (2000) 2541. (c) N. S. Perch, R. A. Widenhoefer, J. Am. Chem. Soc. 126 (2004) 6332. (d) R. A. Widenhoefer, Ace. Chem, Res. 35 (2002) 905. [6] S. Park, D. Takeuchi, K. Osakada, J. Am. Chem. Soc. in press. [7] (a) L. K. Johnson, C. M. Killian, M. Brookhart, J. Am. Chem. Soc. 117 (1995) 6414. (b) C. M. Killian, D. J. Tempel, L. K. Johnson, M. Brookhart, J. Am. Chem. Soc. 118 (1996) 11664. (c) D. J. Tempel, L. K. Johnson, R. L. Huff, P. S. White, M. Brookhart, J. Am. Chem. Soc. 122 (2000) 6686. (d) D. P. Gates, S. A. Svejda, E. Onate, C. M. Killian, L. K. Johnson, P. S. White, M. Brookhart, Macromolecules 33 (2000) 2320. [8] T. N. Choo, R. M. Waymouth, J. Am. Chem. Soc. 125 (2004) 8970.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

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Synthesis of Polymeric Radical Scavengers via ROMP of Norbornene Derivatives and Their Antioxidation Activities Kogen Horikawaa, Katsuya Maeyama3 and Akinori Toyota" "Graduate School of Engineering, Tokyo University of Agriculture and Technology, 224-16 Naka-cha, Kaganei, Tokyo 184-8588, JAPAN

Abstract We studied on polymerization behavior of norbomene derivatives containing 3,5~di~ferf-butyl-4-hydroxybenzoyl (DBH) groups via ring-opening metathesis polymerization (ROMP) and radical scavenging activities of the resulting polymers. New norbornene derivatives containing DBH group, i.e., 5,5BBHBN (2) and 5,6-BBHBN (1) as shown in Fig, 1 were synthesized, ROMP of these norbomene derivatives were performed by using of ruthenium trichloride hydrate and Grubbs catalyst. In order to measure radical scavenging activities (RSA) of the homopolymers and copolymers of the norbornene derivatives, cast films of the polymers were contacted with DPPH-methanol solution, RSA values of poly(5,5-BBHBN) and poly(5,6-BBHBN) were twice or more as high as those of poly(BHBN). 1. INTRODUCTION The polymeric radical scavengers are desired as easily separable antioxidant or as films having antioxidation activity. Tlenkopatchev and co-workers reported homopolymerization and copolymerization of norbomene with norbomene derivatives having 3,5~di-ferf-butyl~4-hydroxybenzoyl (DBH) group[l,2]. However, effects of structures of the norbomene derivatives upon the polymerization behavior were not reported. Radical scavenging activities of the polymers having DBH groups were not also reported.

206

K. Harikawa et al.

We would like to report studies on the ROMP behaviors of 5,5-BBHBN and 5,6-BHBN, and the radical scavenging activities of the resulting polymers from both new monomers. 2. EXPERIMENTAL Two new norbornene derivatives containing two DBH groups, 5,5BBHBN(2) and 5,6-BBHBN(l) were synthesized via esterification reaction (Fig. 1) of alcohols having norbornene rings with 3,5-di-tert-butyl-4-hydroxybenzoyl chloride(4). BHBN(3), having one DBH group, was also synthesized. These norbornene derivatives were homopolymerized and copolymerized with norbornene by using Grubbs catalyst (bis(tricyclohexylphosphine) benzylidene ruthenium dichloride) and ruthenium trichloride hydrate. The resulting homopolymers and copolymers were purified with reprecipitation. In order to measure of radical scavenging activity, cast films (1.4 mg) of the polymers were contacted to diphenylpicrylhydrazyl (DPPH)/methanol solution (0.1 mM) for 3 hr. Then absorbance of the DPPH solutions was measured at 515 nm. The radical scavenging activity (RSA) was defined as follows : RSA(%)=(A0-Af)JA0 X 100. In this equation, Ao is initial absorbance of the DPPH solution, Af is absorbance of the DPPH solutions after contact of the films with the solutions.

5,6-BBHBN AiCOCI pyridine. CHjCI; 5,5-BBHBN ArCOCI

.„

^3^

pyridine, THF BHBN

Fig. 1 Synthesis of norbornene derivatives having DBH groups.

3. RESULTS AND DISCUSSION 3.1. Copolymerization behavior of the norbornene derivatives containing DBH group and norbornene Fig. 2 shows relationships between feed composition of norbornene derivatives (5,5-BBHBN, 5,6-BBHBN, BHBN) and the norbomene derivatives content in copolymers. The left plots are the results in the case of ruthenium trichloride hydrate as a ROMP catalyst. On the other hand, the right ones show

34. Polymeric Radical Scavengers via ROMP of Norbomene Derivatives

207

the results in the case of Grubbs catalyst. In the former, conversion of 5,5BBHBN and 5,6-BBHBN were lower than that of BHBN. This is, probably, due to steric hindrance of 5,5-BBHBN and 5,6-BBHBN. Chelation of the two norbomene derivatives to the ruthenium center occurs presumably. In the latter, fed 5,6-BBHBN and BHBN were almost copolymerized with norbomene. However, copolymerizability of 5,5-BBHBN was inferior to those of 5,6-BBHBN and BHBN. When the norbomene derivatives containing an oxygen atom is polymerized by Grubbs catalyst, coordination of the oxygen atom to ruthenium center occurs and causes the decrease of polymerization rate of the oxygen-containing norbomene derivatives [3,4]. In the case of 5,5BBHBN, the coordination to the ruthenium center causes lowering of copolymerizability possibly.

5

EC -

1UU

1 D 5,5-BBHBN O 5,6-BBHBN o BHBN

0

£S :

>)

it is

1

a

'

5,5-BBHBN O 5,6-BBHBN O BHBN

o o

H

D

40 -

40 -

3

1j

n 0

O n

Q

20

40

SO

SO

2C -

100

Norbornene derivatives in feed (mol%)

(b)

)C

20

40

50

80

LOO

Norbomeiic derivatives m feed (mcl%)

Fig. 2 Norbornene derivatives content in copolymer as a function of feed monomer composition, (a): ruthenium trichloride hydrate, initial monomer cone; 0.41 M, solvent; chlorobenzene, [monomer]/[catalyst]; 33, total volume; 3.4 ml, polymn. temp.; 70 °C, polymn. time; 18 hr (b):Grabbs catalyst, initial monomer cone; 0.35 M, solvent; methylene chloride, [monomer]/[catalyst]; 503, total volume; 4.0 ml, polymn. temp.; r.t., polymn. time; 2.5 hr.

3.2. DPPH radical scavenging activities of the DBH containing polymers Fig. 3 shows RSA values of the norbomene derivatives containing DBH groups and norbomene copolymers obtained with ruthenium trichloride hydrate as a function of their norbomene derivatives contents. The RSA values of the copolymers containing DBH groups depend on their DBH group contents. Fig. 4 shows RSA values of homopolymers of 5,5-BBHBN, 5,6-BBHBN and BHBN obtained with Grubbs catalyst as a function of their number average molecular weight. RSA values of poly(5,5-BBHBN)s and poly(5,6-BBHBN)s were twice or more as high as those of poly(BHBN)s. In particular, RSA values of poly(5,5-BBHBN)s were higher than those of poly(5,6-BBHBN)s.

208

K. Horikawa et at

Configuration sequences of the polymers effect DBH density on the surface of the films possibly. 14 -

-

1

' 5,5-BBHBN O 5,6-BBHBN O BHBN

O

poly(5;0-BBHBN) O pcly(BHBN) ;

20 -

lu -

-

D D

6 -

1

o

40

-

O O

O

&&? ° 20

::

:u -

c 0

1

D poly(5,5-BEIIEN)

60

30

100

Nwbornens derivatives content (mol%)

Fig. 3 RSA values vs. norbomene derivatives content (ruthenium trichloride hydrate).

z

O

105

IT'

Jlij of polymers

Fig. 4 RSA values vs. M homopolymers (Grubbs catalyst).

Of

4. CONCLUSIONS Two new norbomene derivatives containing DBH groups, i.e., 5,5-BBHBN and 5,6-BBHBN, were synthesized. Copolymerization behaviors of these norbomene derivatives and norbomene via ROMP were investigated. RSA values of poly(5,5-BBHBN)s and poly(5,6-BBHBN)s were twice or more as high as those of poly(BHBN)s. References [1] M. A. Tlenkopatchev, E. Miranda, M. A. Canseco, R. Gavino, T. Ogawa, Polym. Bull. 34(1995)385 [2] M. A. Tlenkopatchev, E. Miranda, R. Gavino, T. Ogawa, Polym. Bull. 35 (1995)547 [3] C. Slugovc, S. Demel, S. Riegler, J. Hobisch, F. Stelezer, Macromol. Rapid Commun. 25 (2004) 475 [4] D. M. Haigh, A. M, Kenwright, E, Khosravi, Macromolecules, 38 (2005) 7571

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

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35

Vinyl Polymerization of Norbornene over Supported Nickel Catalyst Junxian Hou, Wenjuan Zhang, Suyun Jie and Wen-Hua Sun* Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China

Abstract The nickel(ll) complex was immobilized onto spherical MgCl2, and performed norbornene polymerization in the existence of MAO. Spherical polymer particle morphology was observed without reactor fouling. 1. INTRODUCTION In recent years nickel-based complexes are becoming one type of important catalysts for vinyl polymerization of norbornene due to their high catalytic activities [1]. We have synthesized various nickel complexes bearing ligands of [N,O] [2] and [P,N] [3] for norbornene polymerization, however, those homogeneous catalysis resulted in a serious fouling of the reactor. The silica, silica-alumina derivatives, MgCl2 [4] and polymeric materials [S] are commonly used as supports. Therefore the immobilization and activation of the nickel complex 1 [2b] benefits the application in norbornene polymerization. 2. EXPERIMENTAL Bis-[JV-(diphenylmethyl)-salicylideneiminato]nickel(Il) (1) [2] and spherical MgCl2"nEtOH [4a, 6] were prepared according to the literature. Morphologies of the PNB particles, the catalysts were examined on a HITACHI S-4300 scan electron microscope. Elemental analysis was performed by spectrophotometry Shimadzu UV-2401PC and titration technique. Nitrogen adsorption-desorption isotherms were measured at 77 K using an ASAP2010 volumetric adsorption

210

J.Houetal

apparatus. Molecular weights were determined by Waters Alliance GPCV 2000 system at 135 °C in 1,2,4-trichlorobenzene. Viscosity measurements were carried out in chlorobenzene at 25 °C using an LJbbelohde viscometer. Typical preparation of MgCl2 supported nickel catalyst 6: To 40 ml hexane solution containing 4.64 g spherical MgCl2-2.97C2HsOH (20.0 mmol) in a 500 ml four-necked flask, 42.9 ml toluene solution of 1.4 M MAO was added over a period of 30 min, and reacted at -30 °C for 4 h. The slurry was filtered under N2 and the solid was washed twice by »-hexane (30 ml x2), dried under N2. The resulting powder was placed in the flask containing 30 ml toluene and the slurry was stirred at 25 °C, 50 ml toluene containing nickel complex 1 (0.22 mmol) was added to the slurry and stirred for 4 h. The final product was washed with toluene, until the liquid layer above became colorless. The solid catalyst (SNC1) was dried in vacuo until free flowing conditions were reached. Polymerization of norbornene: In a 100 mL Schlenk tube, the Ni catalyst (5 umol Ni), 14.08 mL toluene and 3.78 mL solution of norbomene in toluene (6.61 M) were introduced. The polymerization was initiated by addition of a 7.14 mL toluene solution of 1.4 M MAO via syringe. After 60 min, the reaction was terminated by pouring into 200 mL acidic MeOH (MeOH:HClBOTlc= 95:5). 3. RESULTS AND DISCUSSION Effects of supporting conditions: Elemental analysis, surface areas of the supported catalysts are shown in Table 1. Treatment of spherical MgCl2*nEtOH adduct produces dealcoholization without structure collapse [6]. The results indicate that Al loading on the support greatly decreased upon decreasing of the ethanol content in the MgCl2/ethanol adducts. The Ni loading increased in the order of SNC-1 < SNC-2 < SNC-3 < SNC-4. The BET surface areas and pore volume increased upon decreasing the ethanol content in its MgCl2 adduct. There was no significant change in polymer molecular weight relying on various ratio of EtOH to MgCl2 in the range of 1.50-1.98x10* g/mol. The catalytic activities are in the range of 238-281 kg PNB/mol Nrh. SNC-2 was chosen for study in detail at different conditions for its good morphology. Effects of polymerization conditions: Lower activity was observed in hexane while higher activity was obtained in toluene. However, higher molecular weights of the resulted PNBs were obtained in hexane as solvent. Increase of monomer concentration, the M/Ni ratio (M: norbomene), causes rapid increase of the activities combined with a drastic increase of molecular weight. Morphology of the PNB particles changed gigantically with monomer concentration. At an M/Ni ratio of 10000:1, polymer particle started to agglomerate along with reactor fouling, and therefore morphological control was gradually lost.

35. Vinyl Polymerization

ofNorbornene

over Supported Ni Catalyst

211

Table 1 Element analysis and BET analysis of supported catalysts Catalyst

BET ^ ^

Pore vol. ( m L / 8)

Average pore Diameter (A)

7.65

1.5

0.018

477

16.22

5.12

5.4

0.022

162

0.24

16.87

3.60

12.3

0.047

152

0.26

21.52

3.49

18.7

0.093

198

Starting

Ni

Mg

Al

material

wt.%

wt.%

wt.%

SNC-1

MgCl2-2.97Et0H

0.18

10.32

SNC-2

MgCl2-1.72EtOH

0.23

SNC-3

MgCl2'1.30EtOH

SNC-4

MgCl2-0.38EtOH

The treating spherical MgCl^ support with MAO was carried out at -30°C. Table 2. Polymerization of norbornene with supported l a Entry

Catalyst

M/Ni

Yield

Activity11

E

SNC-1

5000

59.7

MJMn

(dL/g)

g/mol)

281

1.06

16.1

4.91

% 1

M w (xl0 s

2C

SNC-1

5000

50.6

238

1.11

18.7

3.85

3

SNC-2

5000

56.9

268

1.10

19.8

5.70

4

SNC-3

5000

53.7

253

0.94

15.2

4.97

5

SNC-4

5000

51.6

243

0.96

15.0

5.76

6

SNC-2

2500

32.2

76

0.77

9.01

4.19

7

Ni(II)

2500

58.2

136

0.65

3.54

3.17

d

8

SNC-2

7500

83.3

5S8

1.39

n.d

n.d.

9

SNC-2

10000

65.9

621

1.48

n.d.

n.d.

Condition: 5 jimol Ni; 25°C; toluene; 60 min; total volume, 25 mL; M / Ni = 5000 ; MAO, Al/Ni = 2000." kg PNB/mol Nrh. c Hexane as solvent. d Not determined.

The activity of the heterogeneous catalyst is ca. 50-70% of its homogeneous catalyst under the same conditions (entry No 6, 7) in Table 2, which is a wellknown phenomenon [7-10] in olefm polymerization. However, comparing entries 6 and 7, the molar mass of the polynorbornene obtained with SNC-2 was around two times higher than that obtained with the homogeneous catalyst 1. The broadening of the molecular weight distributions was evident with the supported catalyst systems. Often the PDI values in the literature are higher for supported catalysts compared to homogeneous system [4b, 7]. Microscopy studies: Fig. la showed that spherical MgCl2-2.97EtOH had a smooth and less porous surface. The supported catalyst (Fig. lb) appeared a rough and porous surface. Fig. lc showed its PNB particle with 15-20 times larger than that of the catalyst SNC-2 (typical 30 um).

212

J. Hou et al.

Fig. 1. SEM micrographs, (a) spherical MgClz-2.97Et0H (600x), (b) SNC-6 (600x), (c) PNB particles (entry 11, 40x).

4. CONCLUSIONS Bis-[N-(diphenylmethyl)-salicylideneiminato]nickel(IT) (1) was supported on spherical MgCl2. The supported catalysts performed well for norbornene polymerization with fine morphology and high activity. The polynorbornenes produced with supported catalyst have higher molecular weight and broader molecular weight distribution than those of its homogeneous ones. Acknowledgements The project supported by NSFC 20473099. This work was partly completed in Polymer Chemistry Laboratory, Chinese Academy of Sciences and China Petro-Chemieal Corporation. References [1]

B. Berchtold, V. Lozan, P-G. Lassahn, C. Janiak, J. Polym. Sci. Polym. Chem. 40 (2002) 3604. [2] H.Yang, W.-H. Sun, F. Chang, Y. Li. Appl. Cat. A. 252 (2003) 261. [3] H. Yang, Z. Li, W.-H. Sun. J. Mol. Catal. A: Chem. 206 (2003) 23. [4] a) R. Huang, D. Liu, S. Wang, B. Mao, Macromol. Chem. Phys. 205 (2004) 966; b) H. S. Cho, W. Y. Lee, J. Mol. Catal. A. 191 (2003) 155. [5] T. R. Boussie, V. Murphy, K. A. Hall, C. Coutard, C. Dales, M. Petro, E. Carlson, H. W. Turner, T. S. Powers, Tetrahedron 55 (1999) 11699. [6] P. Sozzani, S. Bracco, A. Comotti, R. Simonutti, I. Camurati, J. Am. Chem. Soc. 125(2003)12881. [7] F. AlObaidi, Z. Ye, S. Zhu, Macromol. Chem. Phys. 204 (2003) 1653. [8] S. Collins, W. M. Kelly, D. A. Holden, Macromolecules 25 (1992) 1780. [9] M. O. Kristen, Top. Catal. 7 (1999) 89. [10] S. I. Woo, Y. S. Ko, T. K. Han, Macromol. Chem. Phys. 16 (1995) 489.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

213

36 Effect of Catalyst Loading in Olefin Polymerization Catalyzed by Supported Half-Titanocenes on Polystyrene through Phenoxy Linkage Boonyaraeh Kitiyanan and Kotohiro Nomura* Graduate School of Materials Science, Nora Institute of Science and Technology 8916-5 Takayama, Ikama, Nora 630-0101, Japan

Abstract Half-titanocenes immobilized on the poly(styrene-eo-hydroxystyrene) at various Ti loading have been prepared by the reaction with Cp*TiMe3. Effect of catalyst loading toward both the activity and the polymerization behavior was explored, and the catalysts at low Ti loading showed higher activity for ethylene polymerization. These catalysts also produced syndiotactic polystyrene with the moderate activity. However, the significant decrease in the activity was observed in the ethylene/1-hexene copolymerization, affording low molecular weight polymers. 1. INTRODUCTION Design and synthesis of efficient 'heterogeneous single-site catalysts" attract particular attention not only from scientific but also from practical viewpoints [1,2]. This is because most of newly developed transition metal complex catalysts are homogeneous [3,4], and the catalysts should be heterogenized by supporting on to a carrier such as inorganic solids or polymers in order to achieve commercial significance in the current gas or slurry polymerization processes [1,2]. Although several supports such as magnesium chloride, silica, alumina, clay, zeolite, polymers were known [1,2], we focused on polymer or dendrimer supported catalysts [5,6,7], not only because there are practical concerns in using homogeneous catalysts such as separation of the products

214

B, Kitiyanan andK. Nomura

from the catalyst and ligand [8], but also because these supported catalysts play a crucial role in combinatorial and parallel synthesis. Since (aryloxo)(cyclopentadienyl)titanium complexes exhibited high catalytic activity and unique characteristics for olefin polymerization [9] particularly for ethylene (co)polymerizations [10-15], we, therefore, have an interest to prepare the supported complex on polystyrene through phenoxy linkage and explore the possibility of using catalyst precursor for olefin polymerization. 2. EXPERIMENTAL All experiments were carried out under a nitrogen atmosphere in a vacuum atmospheres drybox unless otherwise specified. Anhydrous grade toluene (Kanto Chemical Co., Inc.) was transferred into a bottle containing molecular sieves (mixture of 3A, 4A 1/16, and 13X) in the drybox, and was used without further purification. MAO was prepared by removing toluene and AlMes in vacuo (in the drybox) from the ordinary MAO (PMAO-S, Tosoh Finechem Co.). Other chemicals, such as reagent grade acetoxy styrene, azobisisobutyronitrile (ALBN), were used as received. Polymerization, isolation procedures were according to our previous reports [11,12,16], and molecular weights and molecular weight distributions for resultant polymers were measured by GPC (Tosoh HLC-8121GPC/HT) with polystyrene gel column (TSK gel GMHHR-H HT x 2, 30 cm x 7.8 mni(|> ID), ranging from <102 to < 2.8x10" MW) at 140 °C using o-dichlorobenzene containing 0.05 wt/v% 2,6-di-tert-butyl-p-cresol as solvent. The molecular weight was calculated by a standard procedure based on the calibration with standard polystyrene samples 2.1. Synthesis of polymer supported half-titanocene The polymer supported catalysts were prepared according to Scheme 1. Poly(styrene~eo-hydroxystyrene)s (HPS) were prepared according to a reported procedure [17]: synthesis of poly(styrene-eo-acetoxystyrene) by copolymerization of styrene and 4acetoxystyrene in the presence of AIBN and subsequent hydrolysis using hydrazine hydrate. The contents of acetoxystyrene were estimated by

{ ) 12.3 (B), 21.0(C)moI%. Scheme 1

OH

36. Effect of Catalyst Loading in Polymerization by Supported Half-titanocenes

215

*H NMR spectra. HPS pretreated by removing moisture and oxygen was then dissolved in toluene in the drybox and Cp*TiMe3/toluene solution (1,5 eq) was added slowly into the mixture [10]. The solution was left stirring overnight for completion. Toluene was then removed in vaeuuo and the polymer complex was then recovered by precipitation in «-hexane. In order to remove the excess Cp*TiMe3, this step was repeated until the hexane solution became clear and colorless. The washing hexane solution was then dried and the excess Cp*TiMe3 confirmed by *H and 13C NMR spectra was recovered and weighted. The prepared supported catalysts were identified by 'H, 13C NMR spectra and XPS spectra. 3. RESULTS AND DISCUSSION 3.1. Synthesis and characterization of polymer-supported catalysts. Poly(styrene-eo-hydroxystyrene)s (HPS) were focused on this study, because the reaction of phenol with Cp*TiMe3 should take place exclusively affording the desired Cp*-phenoxy titanium dimethyl complex [10]. 1.5 equiv. of Cp*TiMe3 (based on the acetoxy contents in the copolymers estimated by ] H NMR spectra) was added to a toluene solution containing HPS, and rather excess amount of the Ti complex was used for preparing the dimethyl species, Cp'TiMe2(OAr), exclusively, and Cp*TiMe3 was removed by treating with hexane several times until the solution became colorless as well as until no resonances ascribed to the trimethyl complex were observed in both ]H and 13C NMR spectra. Moreover, removal of hexane from the solution combined the filtrate with the wash, the remaining solid was weighted and found to be equal amount to the unreacted excess (0.5 equiv.) Cp*TiMe3 confirmed by the 'H and 13 C NMR spectra. These results clearly indicate that all phenoxy groups in the HPS were completely reacted with Cp*TiMe3. Selected results for characterization of the polymer-supported catalysts are summarized in Table 1, and typical XPS spectrum of the catalysts is shown in Figure 1. The XPS spectrum clearly showed the presence of Ti in the catalysts, and the binding energy of Ti 2p3/2 900 800 700 600 500 400 300 200 103 level of the catalysts is Bird rig Energy (eV) around 457.5 eV. This value Figure 1. Wide scan and narrow scan for Ti region is the analogous to that in (inset) XPS spectrum of catalyst C. 1000

216

B. Kitiyanan andK, Nomura

Cp2TiCl2 [18], strongly suggesting that the similar electronic environment could be formed around titanium. Resonance ascribed to Ti-Me in 13C NMR was significantly shifted from 61.2 ppm (Cp*TiMe3)to 53.8 ppm, suggesting that Cp*TiMe3 was chemically tethered to the polymer support. Moreover, single resonance for Ti-CH3 as well as the above analysis for remained solid in the wash clearly indicates that no crosslinking/bridging were occurred between the polymer support and the half-titanoeene, as reported by the reaction with Cp*TiCl3[17]. Table 1. Selected results for characterization of the polymer supporting catalysts. _ , Catalysts

, , a , nA M>10

,, „ ., MJMJ1

Binding Energy of _.. ._„ Ti2p 3/2 (eV)

A

6.40

1.9

B

5.67

C

10,67

13

C NMR chemical shift (ppm) e Ti-CH3

C5(CH3)5

457.515

53.8

11.6

1.6

457.5

53.8

11.6

2.1

457.3

53.8

11.6

"GPC data in THF vs polystyrene standards. "Ref. CpzTiCl2 = 457.5 eV [18]. I n C6D6, ref.: ); Ti-CHj 54.2 ppm, Cs(CH3)s 11.4 ppm.

3.2. Olefin polymerization by polymer-supported catalysts. The prepared catalysts showed moderate catalytic activities for ethylene polymerization in the presence of MAO (Table 2), and the activity increased in the order; A > B > C. This suggests that the density of active species in the polymer support plays an essential role toward the catalytic activity for ethylene polymerization. The Mw for resulting polyethylene prepared by A-C were relatively low, and the molecular weight distributions by A-B were narrow (M/M,, = 2.1-2.3). The unimodal molecular weight distributions suggest that the present polymerization took place with single catalytically-active species. However, it should be noted that the activity in the ethylene/1-hexene copolymerization were significantly lower than those in the ethylene homopolymerizations (entry 5-8). The resultant polymers in the ethylene/1hexene copolymerization also possessed low Mw values with broad distributions. A-C showed relatively high catalytic activities for syndiospecific styrene polymerization, affording relatively high molecular weight polymers with unimodal distributions (My/Mn = 2.3-2.4). The results also suggest that the present polymerization took place with a single catalytically-active species. The activity increased in the order: A > B > C. As expected from our previous report [16], the activity increased at higher polymerization temperature.

36, Effect of Catalyst Loading in Polymerization by Supported Half-titanocenes

217

Table 2. Polymerization results of polymer-supported catalysts,11 entry

activity11

Mwc

cat.

ethylene

(co)monomer

temp

(jimol)

/atai

(mL)

/QC

1

A(0.5)

6

-

25

5029

4.97

2.1

2

B (0.5)

6

-

25

3630

5.74

2.3

3

C(0.5)

6

-

25

1664

3.38

3.5

4

C (0.25)

6

-

25

1796

4.66

3.0

5

A (5.0)

6

1-hexene (5)

25

408

0.73

broad

6

A(1.0)

6

1-hexene (1)

25

1950

2.58

2.9

7

B (5.0)

6

1-hexene (5)

25

475

0.81

7.7

g

C(5.0)

6

1-hexene (5)

25

301

0.65

broad

xlO"4

9

A (5.0)

-

styrene (10)

40

224

15.2

2.6

10

A (5.0)

-

styrene (10)

55

325

13.1

2.3

11

A (5.0)

-

styrene (10)

70

1340

22.6

2.4

12

A (5.0)

-

styrene (10)

85

2282

22.0

2.4

13

B (5.0)

-

styrene (10)

55

237

12.9

2.3

14

C(5.0)

-

styrene (10)

55

235

11.8

2.3

"Polymerization conditions: toluene + (eo)monomer total 30 mL, 10 rnin, MAO 3.0 mmol. *Activity in kg-polymer/(mol-Ti'h). CGPC data in o-dichlorobenzene vs polystyrene standards.

4. CONCLUSIONS Cp*TiMes were successfully reacted with phenol in poly(styrene-cohydroxystyrene)s to afford polystyrene supported Cp*-aryloxo titanium dimethyl complexes in high yields, and the resultant solids were identified as monophenoxo species as a sole supported complex. These complexes showed moderate catalytic activities for both ethylene polymerization and syndiospeeiflc styrene polymerization, and the activities increased in the order: A > B > C, suggesting that a certain percentage of the catalytically species would be covered by other titanium species which will lead to decrease the total catalytic activities or broaden the molecular weight distributions. We believe that the present results are important to design better catalyst toward heterogeneous single-site catalyst for precise olefin polymerization.

218

B, Kitiyanan and' K. Nomura

Acknowledgements Part of this research was supported by Grant-in-Aid for Exploratory Research (No. 16656248), and B. Kitiyanan would like to express his sincere appreciation to Japan Society for the Promotion of Science for the postdoctoral fellowship (P05157). K. Nomura would like to thank Tosoh Finechem Co. for donating MAO (PMAO-S). References [I]

J. R. Severn, J. C. Chadwick, R. Duchateau, N. Friederichs, Chem. Rev. 105 (2005) 4073. [2] G. G. Hlatky, Chem. Rev. 100 (2000) 1347. [3] G. J. P. Britovsek, V. C. Gibson, D. F. Wass, Angew. Chem., Int. Ed. Engl. 38(1999)429. [4] V. C. Gibson, S. K. Spitzmesser, Chem. Rev. 103 (2003) 283. [5] D. E. Bergbreiter, Chem. Rev. 102 (2002) 3345. [6] P. H. Toy, K. D, Janda, Ace. Chem. Res. 33 (2000) 546. [7] R. M. Crooks, M. Zhao, L. Sun, V. Chechik, L. K. Yeung, Ace. Chem. Res. 34(2001)181. [8] For example: D. E. Bergbreiter, Catal. Today 42 (1998) 389. [9] K. Nomura, N. Naga, M. Miki, K. Yanagi, A. Imai, Organometallics 17 (1998)2152. [10] K. Nomura, N. Naga, M. Miki, K. Yanagi, Macromolecules 31 (1998) 7588. [II] K. Nomura, K. Oya, Y. Imanishi, J. Mol. Catal. A 174 (2001) 127. [12] K. Nomura, H. Okumura, T. Komatsu, N. Naga, Macromolecules 35 (2002)5388. [13] W. Wang, M. Fujiki, K. Nomura, J. Am. Chem. Soc. 127 (2005) 4582. [14] K. Nomura, K. Itagaki, M. Fujiki, Macromolecules 38 (2005) 2053. [15] K. Nomura, K. Itagaki, Macromolecules 38 (2005) 8121. [16] D.-J. Byun, A. Fudo, A. Tanaka, M. Fujiki, K. Nomura, Macromolecules 37 (2004)5520. [17] R. M. Kasi, E. B. Coughlin, Macromolecules 36 (2003) 6300, [18] F. Garbassi, L. Gila, A. Proto, J. Mol. Catal. A 101(1995) 199.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

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37

Theoretical Study on Active Site Formation of Olefin Metathesis and Olefin Polymerization in Phillips CrOx/SiO2 Catalyst by PIO Analysis AMnobu Shiga"**, Boping Liub and Minoru Teranob "LUMMOXResearch Laho. Takezono 2-18-4-302, Tsukuba, 305-0032, Japan 1 'School of Material Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai,Nomi, Ishikawa, 923-1292, Japan

Abstract Reaction pathways of active site formation on Phillips CrOx/SiO2 catalyst was investigated by paired interacting orbitals (PIO) method using chromic acid as a simple model. A novel mechanism in terms of a transformation from metathesis to polymerization was proposed. Keywords: Phillips catalyst; Olefin metathesis; Olefin polymerization; Paired interacting orbitals (PIO) 1. INTRODUCTION

Though many experimental and theoretical studies have been reported, mechanism of active site formation of Phillips CrOx/SiO2 catalyst is still vague, [1] We have reported that formaldehyde, propylene and butene are formed during the induction period of industrial Phillips catalyst. [2] Here, we investigate the reaction pathways of the formation of active sites, propylene and butene which are given in Eq. 1 - Eq. 4 by using "Paired Interacting Orbitals" (PIO) analysis proposed by Fujimoto et al.[3] (O)2CrLn + C2H4 -^Cr Ln + 2H2CO (1) CrLn + 2C2H4 ^Cr(CH 2 ) 4 L n (2) (3) Cr(CH2)4Ln^Cr(Me(CH2CH2CH2))L11 ^(CH 2 )CrL n + CgHg (4)

A. Shiga et al.

220

2. MODELS AND CALCULATION METHODS We employed chromic acid as the most simple model of the catalyst precursor. The structures of reagents and reactants were optimized by RHF method (STO minimal basis sets) using PC GAMESS developed by Dr. Alex A. Granovsky of the Laboratory of Chemical Cybernetics at Moscow State University. [4] For PIO analysis extended Hiickel MOcalculation was carried out. The extended Htickel parameters are given in Appendix, All calculations were executed on LUMMOX™ system. [5] 3. RESULTS 3-1 Cr(OH)2 formation We assumed the reaction path of Eq. 1 as follows ; 1) as approaching the ethylene molecule to the chromic acid, the distance between the two terminal oxygen atoms of the acid is widening, 2) the ethylene asymmetrically coordinates to the Cr atom, 3) the distance between the C a and the Cp of the ethylene is elongating, 4) the Ca - Cp bond is breaking and forming one CH2O molecule and the CH^-Cr bond 5) the distance between the CH2 moiety and the other terminal oxygen is shortening and the second CH2O molecule is forming. The snapshots of these procedures are shown below.

(1-5) (1-6) (1-7) Fig, 1 The snapshots of the reaction path of Cr(OH)2 formation

37, Theoretical Study on Active Site Formation in Phillips CrOJSiOj Catalyst

221

The PIO analysis is a method for unequivocally determining the orbitals which should play dominant roles in chemical interactions between two systems, [A] and [B], which are constructing a combined system [C], Here, [A] is chromic acid and [B] is ethylene. The most important interaction between [A] and [B] is represented in PIO-1. Contour maps of PIO-1 of each state are shown in Fig. 2. We can see a large in-phase overlap between the chromic acid moiety and the incoming ethylene all along the reaction path. This suggests that though the Eq. 1 is endothermic in STO-3G calculation (62.7kcal/mole), the formation of Cr(OH)2 is plausible. Once Cr(OH)2 is formed the Eq. 2 takes place exothermically (81.6kcal/mol) and then, the formation of chromacyclopentane is easy.

(1-5) (1-6) (1-7) Fig. 2 Contour maps of PIO-1 of each state along Cr(OH)j formation path

3-2 Rearrangement of chromacyclopentane to chromamethylcyclobutane We assumed the reaction path of Eq. 3 as follows; 1) first the zig-zag cyclopentane ring change to the planar ring, 2) P-hydrogen atom moves on the ring plane, 3) approaching to the a-carbon atom, the Cr-Ca bond is breaking. Contour maps of PIO-1 of each state of above procedures are shown in Fig. 3. We can see in Fig. 3 that an in-phase overlap between the moving hydrogen atom and the a-carbon atom increases along the reaction path. From this, we estimated that whereas the rearrangement of

222

A.SMgaetal

chroma-cyclopentane to chromamethylcyclobutane endothermic (12.5kcal/mol), this rearrangement is easy.

(2-1)

(2-2)

is

slightly

(2-3)

Fig. 3 Contour maps of PIO-1 of each state along rearrangement path to chromamethylcyclobutane

3-3 Rearrangement of chromacyclopentane : Cr(CH2)4(OH)2, to vinylethylchromiumhydride : Cr(H)(CH2=CHCH2CH2))(OH)2 We assumed the same procedures as shown in paragraph 3-2. Here, Phydrogen atom on the ring plane approaches to the Cr atom. The contour map of PIO-1 of this state is shown in Fig. 4. A large in-phase overlap is observed in the region between the hydrogen atom and the Cr atom. After this the H-Cr bond is formed and the Cr-Ca bond is broken simultaneously.

(2-1)

(3-2)

Fig. 4 Contour maps of PIO-1 of an intermediate state along rearrangement path to Cr(H)(CHi=CHCH2CH2))(OH)j

From this, we estimated that whereas the rearrangement of chromacyclopentane to vinylethylchromiumhydride is fairly endothermic (50.2kcal/mol), this rearrangement is possible.

37. Theoretical Study on Active Site Formation in Phillips CrO/SiOj Catalyst

223

4. DISCUSSION

A mother active site: Cr(OH)2 is formed by the reduction of chromic acid with one ethylene molecule. Reacting with two ethylene molecules the mother active site turns into chromacyclopentane exothermically(81.6keal/mole). Starting from chromacyclopentane, there are three reaction pathways. 1) The first one is rearrangement to chromamethylcyclobutane through p-hydrogen shift to a-carbon and then, propene and methylidenCr(OH)2 are generated. After that methylidenCr(OH)2 works as a metathesis catalyst. 2) The second one is rearrangement to vinylethylchromiumhydride through P-hydrogen shift to Cr atom. This chromiumhydride may subsequently give ethyl(vinylethyl)chromium by ethylene insertion into the chromiumhydride bond. Espelid et al have reported that an activation energy of ethylene insertion into the chromium—alkyl bond of dialkylchromium species is rather large in comparison with that of conventional Cossee polymerization based on DFT calculation. [6] Therefore, the above mentioned chromium-hydride may be excluded from a candidate of the polymerization active site. 3) The third one is butene-1 generation through the decomposition of the vinylethylchromiumhydride. An original mother active site: Cr(OH)2 is also regenerated in the decomposition. 5. CONCLUSIONS We investigated the reaction pathways of the formation of active sites of Phillips catalyst employing chromic acid as the most simple model of the catalyst precursor. By using the combination of the optimization with RHF STO-3G calculation and PIO analysis followings were estimated: 1) Reduction of a catalyst precursor, chromic acid, by ethylene generates a mother active site, Cr(OH)2. 2) Chromacyclopentane is easily formed by the addition of two ethylene molecules to the mother active site. 3) Rearrangement of chromacyclopentane into chromamethylcyclobutane takes place easily. After this, propylene is produced by metathesis. 4) Rearrangement of chromacyclopentane into vinylethylchromiumhydride also takes place, Butene-1 is generated and the mother active site is regenerated by the decomposition of the

224

5)

A. Shiga et al.

chromiumhydride. An elucidation of the candidate of polymerization active site needs further investigation.

Appendix Coulomb Integrals and orbital exponents are listed in Table 1. Table 1 Extended Huekel Parameters Hii(eV) Orbital His C2s C2p O2s O2p Cr4s Cr4p Cr3d

-13.600 -21.400 -11.400 -32.300 -14.800 -8.660 -5.240 -11.220

1.300 1.625 1.625 2.275 2.275 1.700 1.700 4.950 (0.4876)

1.600(0.7205)

References [1] E. Groppo, C. Lambelti, S. Bordiga, G. Spoto, A. Zecchina, Chem. Rev. 105 (2005) 115-183. [2] a) B. Liu, H. Nakatani, M. Terano, J. Mol. Catal. A: Chem. 184 (2002) 387-398; b) B. Liu, H. Nakatani, M. Terano, J. Mol. Catal. A: Chem. 201 (2003) 189-197. [3] H. Fujimoto, T. Yamasaki, H. Mizutani, N. Koga, J. Am. Chem. Soc. 107(1985)6157-6161. [4] http://classic.chem.msu.su/gran/gamess/index.old.html [5] T. Motoki, A.Shiga, J. Comput. Chem. 25 (2004) 106-111. [6] 0 . Espelid, K. J. Bsjrve, J, Catal. 205 (2002) 366-374.

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38

Plausible Mechanism for the Formation and Transformation of Active Sites on Novel Phillips Type Catalyst with New Organo-siloxane Ligand Wei Xia, Boping Liu*, Yuwei Fang, Daqing Zhou, Minoru Terano School of Materials Science, Japan Advanced Institute of Science and Technology, 1-1 Asahidai, Nomi, Fshikawa, 923-1292, Japan, Email: [email protected]

Abstract A novel Phillips type catalyst with ehiral organo-siloxane ligand was investigated for ethylene polymerization in the presence of triethylaluminum (TEA) coeatalyst Plausible mechanism of the formation and transformation of active sites was proposed to rationalize its unique polymerization behavior. Keywords; Phillips catalyst; Ethylene polymerization; Chiral organo-siloxane ligand; Polymerization kinetics; Short chain branches 1. INTRODUCTION Phillips CrOx/SiO2 catalyst is still responsible for more than one-third of the world commercial high-density polyethylene (HDPE) production [1-3]. Further improvements of this catalyst are in high demand in the industrial field but still remained as a challenging work due to poor mechanistic understanding. In our recent work [4], a novel Phillips type catalyst with chiral organo-siloxane ligand was developed for ethylene polymerization in the presence of TEA coeatalyst. The polymerization kinetic curves seemed to be a hybrid type comprised of two types of basic kinetics. The introduction of the chiral organo-siloxane ligand leads to the formation of polymers with bimodal molecular weight distribution (MWD) as well as more short chain branches (SCBs). Proceeded with previous study, an effort in this work was tried to get mechanistic understanding of the formation and transformation of active sites on this novel catalyst.

W.JGa etal.

226 2. EXPERIMENTAL

Details about the preparation of novel catalyst, polymerization and characterization of polymers were described in our previous papers [4-10], A simple explanation was shown here. Reactor system was vacuumed for 2 h before introduction of heptane solvent, TEA and ethylene monomer. Polymerization was initiated after breaking the catalyst ampoule bottle by a steel bar. Real-time ethylene consumption was continuously monitored by an on-line mass flowmeter. Polymerization was stopped by adding ethanol/HCl. Polymers obtained were characterized by 13C NMR and GPC. 3. RESULTS AND DISCUSSION

(a)

(c) 30 60 Polymerization 1ime(min)

90

Figure 1. Polymerization kinetic curves of catalysts with TEA, (a) PC600-S, Al/Cr molar ratio 15.0; (b) PC600-S, Al/Cr molar ratio 22.5; (c) PC600-4S, Al/Cr molar ratio 22.5.

The catalysts named as PC6G0-S (1:1 Cr/Si molar ratio) and PC600-4S (1:4 Cr/Si molar ratio) were used for ethylene polymerization in the presence of TEA. Polymerization kinetic curves seemed to be a hybrid type (as shown in Figure 1) comprised of two types of basic kinetics: one is fast formation and fast decay and the other is slow formation and slow decay, similar with those using PC600 [10] and CO-prereduced PC600 catalyst [5, 9]. According to the analysis of atomic percentage by X-ray photoelectron spectroscopy (XPS) [4], 46.5% of surface Cr

+ 2TEA-CH2O

+ 2TEA-CH2O Site-A

Site-C

y C ^

_L

mTEA *

c I I Site-B

Scheme 1. Plausible mechanism of the formation of two kinds of active sites on Phillips catalyst in the presence of TEA. y=l or 2, m=l or 2

Site-E

Scheme 2. Plausible mechanism of the formation of two kinds of active sites on the novel Phillips type catalyst in the presence of TEA. y=l or 2, m=l or 2

sites connected with the chiral organo-siloxane ligand for PC600-S catalyst. It is reasonable to ascribe the two basic types of kinetics to different types of active

38. Plausible Mechanism for the Formation and Transformation of Active Sites

227

sites. The instant activation and fast decay sites comprised of site-A (in Scheme 1) and site-D (in Scheme 2) were formed through desorption of formaldehyde from Cr(ll) sites (site-C in Scheme 1 and site-F in Scheme 2) by TEA. Site-A and site-D were relatively exposed and could be easily coordinated with ethylene monomer and over-reduced by TEA cocatalyst. Such active sites had higher activity but faster decay. On the other hand, the ehromate Cr (VI) species (as shown in Schemes 1 and 2) were reduced by TEA and coordinated by Alalkoxy (named as site-B in Scheme 1 and site-E in Scheme 2) with slow activation and slow decay. Cr (II) sites strongly coordinating with Al-alkoxy, formed by oxidation of TEA with ehromate Cr (VI) species, were protected from further over-reduction by TEA and influenced by electron donation from Al-alkoxy. So site-B and site-E had low activity and high stability compared with site-A and site-D. For PC600-4S catalyst, 96.3% of surface Cr sites connected with the chiral organo-siloxane ligand [4]. It is reasonable to ascribe the two basic types of kinetics to two different types of active sites (as shown in Scheme 2). The instant activation and fast decay were attributed to site-D. The slow activation and slow decay were attributed to site-E. Table 1. SCBs of polymers obtained from PC600-S orPC600-4S catalysts with TEA cooatalysta

a

Run

Cat.

Ai/Ct

Methyl branches'3

Ethyl branches

Propyl branches

n-Butyl branches

1

PC600-S

15.0

1.37

0.79

0.66

0,50

2

PC600-S

22.5

0.98

0.64

0.53

0.34

3

PC600-4S

22.5

2.63

1.36

0.S3

0.66

b

Polymerization conditions: see reference [4]. Number of methyl, ethyl, propyl or n-butyl branches per 1000 backbone carbon determined by 13C-NMR method.

Microstructures of polymers obtained were shown in Table 1. Formation of SCBs (including methyl, ethyl, propyl and n-butyl) was proposed to be derived from a metathesis reaction on Cr (II) sites coordinated with formaldehyde (siteC in Scheme 1 and site-F in Scheme 2). These metathesis sites can be converted into polymerization sites (site-A in Scheme 1 and site-D in Scheme 2) by desorption of the coordinated formaldehyde. For PC600-S catalyst, the relative amount of SCBs decreased with increase of Al/Cr molar ratio, which was also similar with that of calcined PC600 catalyst [10]. Firstly, there existed a competition between ethylene monomer and TEA to reduce ehromate Cr (VI) species (shown in Schemes 1 and 2) into Cr (II) sites. Secondly, TEA could accelerate the conversion of metathesis sites into polymerization sites. Finally, the kinetic curves of runs 1 and 2 were deconvolved into two types of kinetic curves (ai and a2 for run 1, bi and b 2 for run 2) using same way with our previous works [9, 10]. The weight percentage of polymer obtained from site-A and site-D was calculated by integral area of kinetic curves. The relative content

228

W.Xiaetal

of polymer formed by site-A and site-D decreased from 16.5 to 14.3 wt % with increase of Al/Cr molar ratio from 15 to 22.5. Comparing PC600-S with PC600-4S under the same Al/Cr molar ratio 22.5, it was obvious that the relative amount of SCBs in the polymer obtained from PC600-4S is more than that obtained from PC600-S. The introduction of chiral organo-siloxane ligand seemed to promote the formation of SCBs due to the steric and/or electronic effect. It was further confirmed from the weight percentage of polymer obtained from site-D calculated by integral area of kinetic curves ci in run3 (19.9%). The relative amount of SCBs decreased in the following order: methyl > ethyl > propyl > n-butyl. In situ ethylene metathesis reaction can interpret well the formation of all SCBs and the relative amount of SCBs. For runs 2 and 3, the MW is similar but the MWD of polymer obtained from run 3 is less than that obtained from run 2 [4]. It can be explained that the active sites of PC600-S catalyst (site-A and site-B in Scheme 1, site-D and site-E in Scheme 2) are more complicated than those of PC600-4S catalyst (site-D and site-E in Scheme 2). 4. CONCLUSIONS Plausible mechanism for the formation and transformation of active sites on the novel Phillips type catalyst with chiral organo-siloxane ligand was proposed in terms of deeper mechanistic understanding on its unique polymerization behavior, formation of more SCBs and bimodal MWD. References [I] T. J. Pullukat, R. E. Hoff, Catal. Rev. Sci. Eng. 41 (1999) 389-428. [2] A. Razavi, C.R. Acad. Sci., Serie lie: Chimie 3 (2000) 615-625. [3] M. P. McDaniel, Adv. Catal. 33 (1985) 47-98. [4] Y. Fang, W. Xia, M. He, B. Liu, K. Hasebe, M. Terano, J. Mol. Catal. A: Chem. 247 (2006) 240-247. [5] B. Liu, Y. Fang, H. Nakatani, M. Terano, Macromol. Symp. 213 (2004) 3746. [6] B. Liu, Y. Fang, M. Terano, J. Mol. Catal. A: Chem. 219 (2004) 165-173. [7] Y. Fang, B. Liu, M. Terano, Appl. Catal. A: Gen. 279 (2005) 131-138. [8] B. Liu, P. Sinderlar, Y. Fang, K. Hasebe, M. Terano, J. Mol. Catal. A: Chem. 238 (2005) 142-150. [9] Y. Fang, B. Liu, K. Hasebe, M. Terano, J. Polym. Sci. A: Polym. Chem. 43 (2005)4632-4641. [10] W. Xia, Y. Fang, B. Liu, M. Terano, submitted to J. Mol. Catal. A: Chem. II1] B. Liu, H. Nakatani, M. Terano, J. Mol. Catal. A: Chem. 201 (2003) 189197.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

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39 Influence of polymer morphology on photo-stability of polypropylene/SiO2 nanocomposites Ken-ichi Suminoa, Kazuo Asukaa, Hoping Liua, Masayuki Yamaguchf, MinoruTerano"'*, Takanobu Kawamurab, Koh-hei Nittab "School of Materials Science, JAIST, 1-1 Asahidai, Nomi, Ishikawa, 923-1211, Japan Graduate School of Natural Science and Technology, Kanazawa University, 2-40-20 Kodatuno Kanazawa, 920-3697, Japan

Abstract Effect of polymer morphology on the photo-stability was studied for the nanocomposites of PP and SiO2. It was found from photo-degradation test that the composite without spherulite texture has less carbonyl group, indicating its higher photo-stability than that containing spherulites. 1. INTRODUCTION Increasing interest has been focused on the research and development of novel polymer-based nanocomposites from both scientific and industrial fields [1]. Especially, polyolefm-based nanocomposites are the most perspective from the view-point of the environmental significance. It has been reported that not only the mechanical and thermal properties but many other performances including transparency, fire retardancy and gas permeability could be significantly improved for polyolefin-based nanocomposites compared with original polyolefin materials [2,3]. For polypropylene(PP)-based nanocomposites, most of the researchers used clay as the main nano-filler, while use of SiO2 was seldom reported in the literature up to now. Taking into account of its great abundance on the earth, low cost, high thermal stability as well as surface functionalizabilty, silica gel can be considered to be one of the best candidates for synthesizing various novel polyolefin-based nanocomposites. Moreover, stability of the nanocomposites has been scarcely investigated in spite of the great history on the study of polymer degradation and stability [4-6].

230

K Sumino et at

In this paper, photo-stability of PP/ SiO2 nanocomposites was studied in terms of different morphology of PP to get the basic understanding for the development of highly stable PP materials. 2. EXPERIMENTAL 2.1 Raw materials PP with an isotacticity index (I.I.) of 98%, weight average molecular weight (Mw) of 260000 and molecular weight distribution (Mw/Mn) of 5.6 was donated by Chisso Corp.. SiO2 with an average particle size of 26 nm and surface area of 110m2/g was purchased from Kanto Chemical Co.. 2.2 Preparation ofPP/SiO2 nanocomposites Mixing was performed by two-roll mill, on which the surface temperature was kept at 180 °C. After melting PP, 5wt% of SiO2 was added and blended for lOmin. Then, the obtained mixture was pressed into a flat sheet at 230 °C under a pressure of 100kg/cm2 for 5 min using a compression-molding machine. Two kinds of PP/SiO2 nanocomposites were prepared at the different cooling conditions ; (I) quenched at 100 °C (Sample-I), (II) quenched at 0 °C then annealed at 100 °C for 24h under N 2 (Sample-II). 2.3 Characterization Dispersion states of SiOi nanoparticles in PP matrix were characterized by transmission electron microscope (TEM). Crystallinities of PP in two nanocomposites were analyzed by differetial scanning calorimatry (DSC) method. 2.4 Photo-degradation ofPP/SiOs nanocomposites Photo-degradation experiments were conducted in the weather meter at 35 °C using four 550W Xenon lamps. The degradation was evaluated using carbonyl absorbance measured by FT-IR [1]. 3. RESULTS AND DISCUSSION Figure 1 shows TEM images of Sample-I including 5wt% of SiOz. Almost

39. Polymer Morphology on Photo-stability ofPP/SiOj Nanocomposites

231

homogeneous dispersion state of SiO2 nanoparticles in PP matrixis is observed in spite of the simple mixing procedure. Similar dispersion state can be expected for Sample-11, because the mixing procedure and condition were equal to that of Sample-1. Moreover, the samples were found by DSC measurements to have the same degree of crystallinity of PP, 52%. But, their crystalline textures observed by polarizing optical microscopy (POM) were completely different. Typical sphrulite texture with lOfim was confirmed for Sample-I, while no spherulite was observed in Sample-11.

20

40

60

30

100

Time ( h )

Figure 1 TEM image of PP/SiO^ nanocomposite

Figure 2 Photostability of PP/SiO2 nanocomposites

Figure 2 shows the carbonyl absorbance plotted against the photo-degradation time in the weather meter. The carbonyl absorbances of the samples increase rapidly after ca. 40h. Sample-I shows higher values from the starting point with higher increasing rate. The reason is not clear at this present, but the existence of spherulite texture may have the important role for the phenomena. It will be clarified in our forthcoming reports. 4. CONCLUSIONS Photo-stability of two PP/SiO2 nanocomposites with and without spherulite having the same crystallinity of PP was investigated and found that the

232

K. Sumina et al.

crystalline texture like spherulite has the great effects. This aspect may contribute to the development of highly stable PP materials. References [1] A. Oya, in: Polymer-Clay Nanocomposites, T, J. Pinnavaia, G. W. Beall, Eds. John Wiley & Sons, Ltd, (2000) 151-172. [2] P. Maiti, P. H, Nam, M. Okamoto, N. Hasegawa, A. Usuki, Macromolecules 35,(2002) 2042 [3] B. Liu, K. Asuka, M. Terano, K. Nitta, in: Current Achievements on Heterogeneous Catalysts for Olefin Polymerization, V. Busieo, M. Terano, Eds., Sankeisha Co. Ltd. Nagoya, (2004) 119-126. [4] J. C. W. Chien, D. S. T. Wang: Macromolecules 8(6), (1975) 920. [5] T Hatanaka, H Mori, M Terano: Polym. Degrad. Stab. 64 (1999) 313. [6] Ben G. S.Goss, H. Nakatani, Graeme A. George, M. Terano: Polym. Degrad. Stab. 82(2003)119-126.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

233

40 Photo-oxidation of Polyolefin/Clay Composites Shimin Zhang*, Huaili Qin, Mingshu Yang Key Laboratory of Engineering Plastics, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, P. R. China. E-mail: smzhang@,iccas. ac.cn

Abstract The photo-oxidation behavior of the polyolefin/clay composites is characterized on the basis of the source, type and modification of clays as well as the presence of compatibilizer. It is concluded that the photo-oxidation of polyolefin matrix is mainly due to acidity of clay but less dependent on the dispersion state of the filler. The photo-stabilization of polyolefin using modified clay has discussed. 1. INTRODUCTION Since their discovery in the 1980's [1], polymer/clay nanocomposites have received great attention [2,3]- Today some polyolefin/clay nanocomposites have been also industrially produced and used in certain fields. As the same to conventional polymeric materials, the environmental stability of polyolefin/clay nanocomposites is a key feature in their usage. Due to the presence of clay, the degradation behaviors of polyolefin are dramatically altered [4]. The present paper reports some results on the photo-oxidation of polyolefin/clay composites. 2. EXPERIMENTAL Preparation. Polyolefin/clay composites were obtained by melt compounding of polyolefin and different clays using a twin-screw extruder [5,6]. The samples are described in Table 1. The films (-50 \un) were prepared by blow-molding for PE/clay composites and hot-pressing for PP/clay composites, respectively. Photo-oxidation. For characterizing the photo-oxidation behavior of the polyolefin/clay composites, the films were exposed under UV light (wavelength of radiation: 300 nm) at 45 2°C in a canned UV exposure instrument. The

S. Zhang et at

234

photo-oxidation was followed up by FT-IR spectra in the wave-number range of 4000-370 cm"1, per 40 h upon UV exposure for a period from 0 h to 320 h. The photo-oxidation rate was measured using the area of the carbonyl absorbance (around 1715 cm"1) in the FT-IR spectra. Table 1 Samples descriptions ° PP/CIay composites

PE/CIay composites Sample

Clay

PE

/

PE/Na-MMT PE/SCP PE/Kaolin PE/Si-MMT PE/AO-Si

Na-MMT SCP

b

C

Kaolin

d

Si-MMT

s

AO/Si-MMT

Sample

PPgMA e (wt%)

Clay

CliNh (wt%)

PP

/

/

/

PP/OMMT

/

OMMT'

/

PP/H-MMT

/

H-MMT

j

/

PP/PPgMA

15

/

/

PP/PPgMA/OMMT

15

OMMT

/

f

a

Clay content is fixed to 5 wt% for all composites. Matrixes PE and PP are respectively PE-1I2A and PP-1300 from Yanshan Petrochemical. Modified montmorillonite (MMT) clays were prepared with Na-MMT. Sodium MMT from Zhangjiakou Qinghe Chemical Factory, c Sodium MMT from Southern Clay Products. From China University of Mining and Technology (Beijing). B Trimethylchlorosilane treated MMT. f Antioxidant intercalated Si-MMT. e Maleic anhydride grafted polypropylene. Octadecyltrimethylammonium chloride.' Organoclay by intercalating with dioctadecyldimethylammonium chloride.J Protonated MMT.

3. RESULTS AND DISCUSSION 3.1. Influence of clay type on photo-oxidation ofPE/clay composites Clay minerals are finely crystalline hydrous aluminum silicates and hydrous magnesium silicates. Their diversity in the source, type and chemical composition have different influence on the degradation of the polymer/clay composites. Figure 1 shows the variation of the area of carbonyl band during the photo-oxidation of PE/clay Exposure time (h) composites with different clays. For the same type of sodium MMT, the photo- Figure 1 Influence of clay type on the oxidation rate of PE/Na-MMT and PE/SCP photo-oxidation of PE/clay composites composites reveal changes in the late stage of UV exposure. Kaolinite, which has very low cation exchange capacity but

40. Photo-oxidation ofPolyolefin/Clay Composites

235

more hydroxyl groups at the layer edges compared to sodium MMT, accelerates greatly the photo-oxidation of PE. It is reported [7] that the clay minerals contain various catalytic active sites, such as Bronsted acidic sites like the weakly acidic SiOH and strongly acidic bridging hydroxyl groups at the edges of the clay layers, un-exchangeable transition metal ions in the galleries, and crystallographic defect sites within the layers. These active sites are conducive to the formation of free radicals, leading to the oxidation of the polymer matrix. The present work suggests that the strongly acidic hydroxyl groups at the edges of the clay layers have great influence on the photo-oxidation of polyolefin/clay composites. 3.2. Photo-oxidation

polyolefin/clay

composites

In a previous work [5], we reported the dispersion state of various MMTs in the PP matrix. Both PP/OMMT and PP/H-MMT composites reveal immiscible dispersion of the clays but the former has better dispersion of clay with smaller particle size. With the incorporation of the compatibilizer, PPgMA, the resulted PP/PPgMA/OMMT system is a partially exfoliated nanocomposite. Figure 2 shows the area of carbonyl band in - PP/PPgMA + PP/OMMT - PP/PPgMa/OMMT function of the exposure time for the PP/clay - PF/QMMT PP/H-MMT composites. Although the dispersion state of | ~ i ^P«H-MMT PP/PPgMA clay is different between PP/OMMT and i PP/H-MMT, their photo-oxidation behaviors | are very similar. The degradation rate of the | nanocomposite PP/PPgMA/OMMT is fastest " amongst the PP/clay composites. However, it is observed that the contribution of OMMT exposure time m to the degradation of PP/PPgMA/OMMT is Figure 2 Photo-oxidation of PP/clay well consistent to PP/OMMT if removing the composites influence of PPgMA by comparing to the arithmetical summation of PP/PPgMA and PP/OMMT (the curve with filled symbol). The results suggest that the dispersion state of clay in the PP/clay composite has a little influence on the photo-oxidative degradation of PP matrix. It is in agreement with the photo-oxidation of PE/clay composites reported previously [6]. In fact, due to the Hoffman elimination of alkylammonium in OMMT during the processing and UV exposure [6-8], the acidity of clay filler increases, leading to a catalytic degradation of the matrix. 3.3. Photo-stabilization

using modified clay

Clay minerals, especially of the smectite group like montmorillonite, can host various molecule guests. Therefore, it is possible to intercalate chemicals

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having photo-stabilization effect into the interlayer galleries of clay. By using chemicals with strong interaction to the clay, the migration of the small molecules may be reduced and thus the modified clay could act as a long-term photo-stabilizer for polymers. Figure 3 shows some preliminary results for ^ —PHNa-MMT the photo-stabilization of polyethylene using modified clays. First of all, the pristine Na- j MMT was treated with trimethylchlorosilane 1 for the elimination of hydroxyl groups at the \ edges of the clay layers in order to avoid their j catalytic effect on the degradation of PE. As shown in Figure 3, the degradation rate of the PE/Si-MMT composite decreases in sxpoauretime m comparison to the PE/Na-MMT system. By Figure 3 Photo-stabilization effect intercalating an anti-oxidant in Si-MMT, the of modified clays resulted PE/AO-Si composite does not undergo noticeable degradation and is more stable than pure PE in the test range. 4. CONCLUSIONS The photo-oxidation of polyolefin/clay composites have been investigated in this work. The degradation of the composites is dependent on the source, type and modification of clays. The common alkylammonium modified clay accelerates the photo-degradation; however, the dispersion state of clay has little influence on the photo-oxidative degradation of polyolefin matrix while the acidity of clay plays a key role. By eliminating the acidic sites and incorporating photo-stabilizing chemicals into clay, the photo-stabilizing effect on polyolefin has been demonstrated. Reference! [1] [2] [3] [4] [5] [6] [7] [8]

A. Okada, M. Kawasumi, T. Kurauchi, O. Kamigaito, Polym. Prepr. 28 (1987) 447-44S. S.S. Ray, M. Okamoto, Prog. Polym. Sci. 28 (2003) 1539-1641. F. Gao, Mater. Today 7(11) (2004) 50-55. IK. Pandey, K. Raghunatha Reddy, A. Pratheep Kumar, R.P. Singh, Polym. Degrad. Stab. 88 (2005) 234-250. H.L. Qin, S.M. Zhang, C.G. Zhao, M.S. Yang, J. Polym. Sci. Part B: Polym. Phys. 43 (2005) 3713-3719. H.L. Qin, Z.G. Zhang, M. Feng, F.L. Gong, S.M. Zhang, M.S. Yang. J. Polym. Sci. Part B: Polym. Phys. 42 (2004) 3006-3012. W. Xie, Z. Gao, W.-P. Pan, D. Hunter, A. Singh, R. Vaia, Chem. Mater. 13 (2001) 2979-2990. M. ZanettL, G. Camino, R. Reichert, R. Mulhaupt. Macromol. Rapid Commun. 22 (2001) 176-180.

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41 Effects of Silica Particles on the Transparency of Polypropylene Based Nanocomposites Kazuo Asukaa, Iku Kouzaia, Boping Liua'*, Minoru Teranoa, Koh-hei Nittab "School of Materials Science, JAIST, 1-1 Asahidai, Nomi, Ishlkawa, 923-1292, Japan Graduate School of Natural Sci. and Tech., Kanazawa University, Kakuma, Kanazawa, 920-1192, Japan

Abstract Addition of smaller silica nanoparticles was found to lower the growth rate of PP spherulites more effectively, Spherulite growth rate became zero for PP/16nm-SiO2 nanocomposites with the silica content above 2.5wt%. Consequently, the PP/16nm-SiO2 nanocomposite films showed high transparency compared with PP films. 1. INTRODUCTION Polypropylene (PP) has been regarded as the most promising material in polyolefins to develop new application fields. However, various properties have to be improved to achieve the developments. It has been reported for PP that the mechanical and thermal properties [1,2] as well as many other performances [3] could be significantly improved by forming nanocomposites using various nanoparticles. In this study, the influences of size and content of silica particle on the isothermal growth rate of PP spherulites in various PP/SiO2 composites were tried to characterize using polarized optical microscope equipped with temperature controlled hot stage. Thermal and transparent properties were also evaluated for the nanocomposites.

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2. EXPERIMENTAL Raw materials used and preparation procedures of PP/SiO2 composites are described elsewhere [4,5]. Differential scanning calorimetry (DSC) measurements were carried out under nitrogen using METTLER DSC 820 to examine the isothermal crystallization behavior. Each sample of 2 mg was stored in aluminum pan, heated up to 473K, and quenched to 403K. Spherulite radius was measured as a function of time during the isothermal crystallization process. An optical polarizing microscope fitted with an automated hot stage was used. The hot stage was held at a steady temperature to 2 K by a proportional controller. Thin films of the composites and PP films were sandwiched between a microscope slide and a cover glass, heated to 503 K and kept at this temperature for 10 min to melt completely the crystallites. Then the samples were rapidly quenched to a given crystallization temperature Tc (403 K) and allowed to crystallize isothermally. Haze value and light transmission measurements were carried out using NDH2000 to examine the transparency. 3. RESULTS AND DISCUSSION DSC curves for PP and PP/SiO2 composites are given in Fig.l. It was found the crystallization PP®1nm-SS0j PPSBnm-srOg temperatures of PP/SiO2 composites were almost ^4 PP the same order of that of ^ PP, implying that the silica particle has no ability to act as a nucleating agent of primary crystallization of PP. On the contrary, the 10 15 20 silica particle strongly Time / min affected the secondary Fig.1 DSC curves for PP and crystallization. Fig.2 shows PP/SiOa composites on 403 K the pictures of the spherulite morphology during isothermal crystallization for the PP and PP/SiO2 composites under the optical microscope with crossed polar. As shown in Figs.2 (a) and (b), the morphological texture of PP spherulites in PP/51[im-SiO2 is apparently similar to that of PP. The spherulite growth rate of PP in the

41. Effects of silica particles on the transparency ofPP based ncmocomposites

239

Fig,2 Optical micrographs of spherulites during crystallization at 403 K: (a) PP; (b) PP/51^m-SiO2; (c) PP/100nm-SiO2; (d) PP/26nm-SiO2; (e) PP/16nm-SiOz

nanocomposites (see Figs.2 (c) and (d)) were drastically reduced. It should be noted have that no visible spherulites of PP appeared in the PP/16nm-SiO2. Sphemlite radii of all the samples increase linearly with time over the entire experimental range. As a result, their isothermal spherulite growth rates could be precisely determined from the slope of the lines. The spherulite growth rates at 403 K for PP and PP/SiO2 composites are plotted against the silica content in Fig. 3, The spherulite growth rates of PP in the nanocomposites decrease greatly with increase of 16nm ~ 100nm-SiO2 content. While, the growth rate in the composites using 51(imSiO2 was not changed even the amount of silica increased. It is interesting to note that the addition of smaller silica particles effectively lowered the growth rate of PP SiO 2 content / wt% spherulite in the composites. The growth rate of spherulites became

V

on SiO2 content

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K. Asuka et al.

zero for the 30 PP/16nm-SiO2 nanocomposites with the silica to content above 2.5wt%. The haze value and light transmission for PP and PP/16nm-SiO2 nanocomposites - 65 are plotted against the silica content in Fig.4. As a result, the PP/16nm-SiO2 60 1 3 4 nanocomposite SiO. content / wt% films showed high transparency as Fig.4 Dependence of haze value and light transmission for PP and PP/16nmcompared to PP SiOa on SiOa content films. According to this study, the addition of nano-sized particles to PP will be quite effective technology to prepare transparent materials based on semi-crytalline polymer. 4. CONCLUSIONS Addition of smaller size silica particles was found to lower the growth rate of PP spherulite in nano-composites more effectively. The spherulite growth rate became zero for PP/16nm-SiO2 nano-composites with the silica content above 2.5wt%. Consequently, the PP/16nm-SiO2 nanocomposite films showed high transparency compared with PP films. Therefore, this study may open the real possibility for PP to cover the highly transparent application fields. References [1] A. Usuki, M. Kato, A. Okada, T. Kurauchi, J. Appl. Polym. Sci. 63 (1997) 137-139. [2] Y. S. Thio, A. S. Argon, R. E. Cohen, Polymer 45 (2004) 3139-3147. [3] Y. Deng, A. Gu, Z. Fang, Polym. Int. 53 (2004) 85-91. [4] B. Liu, K. Asuka, M. Terano, K. Nitta, in; M. Terano (Ed.), Current Achievements on Heterogeneous Catalysts for Olefin Polymerization, Sankeisha Co. Ltd. Nagoya, 2004, pp.119-126. [5] K. Asuka, B. Liu, M. Terano, K. Nitta, Macromol. Rapid Commun. accepted.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

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Propene Polymerization by ansaFluorenylamidodimethyltitanium Activated with Si02-Supported Modified Methylalminoxane Takeshi Shionoa*s Takashi Matsumaebi, Kei Nishiibii, Tomiki Ikedab "Graduate School of Engineering, Hiroshima University, Kagamiyama 1-4-1, ffigashiHiroshima 739-8527, Japan, ^Chemical Resources Laboratory, Tokyo Institute of Technology, 4259 Nagatsuta, Yokohama, 226-8503, Japan

Abstract SiO2-supported cocatalyst was prepared from trialkylaluminium-free modified methylaluminoxane. Propene polymerization was performed by [/BuNSiMe2(Flu)]TiMe2 combined with the prepared cocatalyst in heptane. The supported system showed a comparable initial activity to the corresponding homogeneous system that conducts living polymerization of propene and gave the polymer with higher molecular weight and broader molecular weight distribution. Deactivation and chain transfer reaction however occurred in the supported system. 1. INTRODUCTION Development of well-defined transition-metal complex catalysts for olefin polymerization, so-called single-site catalysts, has offered a detailed understanding of the mechanism and stereochemistry of the polymerization [1,2]. In order to apply these systems to existing gas phase and slurry processes, single-site catalysts have to be hydrogenised. In recent years, not a few examples for living polymerization of olefins have been reported by using single-site catalysts [3]. Living polymerization in heterogeneous systems also seems to be interesting from both academic and practical point of view. 1

Present affiliation, JGC Corporation." Present affiliation, Zeon Corporation.

242

T, Shiano et al.

We have previously reported that living polymerization of propene proceeded in heptane at 0 °C by [ArN
42. Propene Polymerization with [t-BuNSiMeJFlu]TiMerMMAO/SiO2

243

propene polymerization was conducted by the corresponding homogeneous system under the same polymerization conditions. The results are shown in Table 1. Table 1 Results of Propene Polymerization by 2 with Various Cocatalysts B Entry

Activator

MJMnb

Yield

Activity

(g)

(kg-PP/mol-Ti/h)

(xlO4)

Ns (Mmol)

1"

dMMAO

2.49

249

18.8

1.26

13

2

e

dMMAO/SiO2

1.36

136

59.6

3.66

2.3

3

f

1-dMMAO

2.68

321

29.2

1.16

9.2

4

s

l-dMMAO/SiO2

1.96

235

66.1

1.34

3.0

a

Polymerization conditions: heptane = 30 mL, Ti = 20 (xniol, propene = 1 atm, temperature = 0 C, time = 30 min, 1 = [ArN(CH2)3NAr]TiMe2 (Ar = 2, 6-'Pr2CgH3). bNumber average molecular weight and molecular weight distribution determined by GPC using universal calibration. c Calculated from yield and Mn. d Al = 8.0 mmol B Al = 4.0 mmol. f Ref. 4. 6 Ref. 5. D

The activity of the dMMAO/SiO2 system was about a half of the corresponding homogeneous system. It should be however noted that the activity of the supported system is almost the same magnitude of that of the corresponding homogeneous system, because it is generally observed that the activity of homogeneous catalyst significantly decreased by heterogenization. The number-average molecular weight (Mn) of the polymer obtained by the dMMAO/SiO2 system was more than three times larger that obtained by the homogeneous system, which suggests the higher propagation rate in the former system. The molecular weight distribution (MJMn) of the homogeneous system was close to one, which indicates the livingness of the system as reported previously [6]. On the other hand, the MJMn values of the SiO2-supported system were around three, which suggests the heterogeneity of the active species and/or the presence of chain transfer reaction. We have already reported that 1 conducted living polymerization of propene both with dMMAO and dMMAO/SiO2 as cocatalyst [5], the results of which are quoted in Table 1. To investigate the kinetic features of the 2-dMMAO/SiO2 system, we conducted propene polymerization by changing the polymerization time, and the results are summarized in Table 2. The activity of the dMMAO/SiO2 system gradually decreased with prolonging the polymerization time, which indicates the deactivation occurred in this system. The Mn value of the produced polymer showed high molecular weight from the early stage of the polymerization and kept constant with the MyJMn value of around 3.5. The number of polymer chains (N) calculated from the polymer yield and the Mn value gradually increased against the polymerization time, which indicates that chain transfer

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also occurred in the 2-dMMAO/SiO2 system. These results are in marked contrast to those of the l-dMMA0/Si02 system reported previously [5]. Table 2 Effects of Polymerization Time in Propene Polymerization by 2—dMMAO/SiOa a Entry

5

Activator

dMMAO/SiOa «

Time

Activity

M?

MJM*

4

(min)

(kg-PP/mol-Ti/h)

(xlO )

5

233

55.6

3.70

0.7

Oioifli)

15

160

65.6

3.27

1.2

7

u

25

160

54.8

3.47

2.4

2

a

30

136

59.6

3.66

2.3

6

a

Polymerization conditions: heptane = 30 mL, Ti = 20 pmol, Al = 4.0 mmol, propene = 1 atm, b temperature = 0 °C Number average molecular weight and molecular weight distribution determined by GPC using universal calibration.c Calculated from yield and Mn,

4. CONCLUSION Propene polymerization was conducted by the titanium complex 2 activated with dMMAO and dMMAO/SiO2 and the results obtained were compared with those by the complex 1. The supporting effects of SiO2 were found to be strongly depended on the titanium complex combined. Acknowledgement! This work was partly supported by a Grant-in-Aid for Scientific Research (No. 15360419) from the Ministry of Education, Culture, Sports, Science and Technology of Japan. References [1] W. Kaminsky, Advances in Catalysis 46 (2001) 89-159. [2] V. C. Gibson, and S. K. Spitzmesser, Chem. Rev. 103 (2003) 283-315. [3] G. W. Coates, P. D. Hustad, and S. Reinartz, Angew. Chem., Inter. Ed. 41 (2002) 2236-2257. [4] H. Hagimoto, T. Shiono, T. Ikeda, Macromol. Rapid Commun. 23 (2002) 73-76. [5] H. Hagimoto, T. Shiono, T. Ikeda, Macromolecules 35 (2002) 5744-5745. [6] K. Mshii, T. Matsumae, E. O. Dare, T. Shiono, and T. Ikeda, Macromol. Chem. Phys. 205 (2004) 363-369. [7] Z. Cai, T. Ikeda, M, Akita, and T. Shiono, Macromolecules 38 (2005) 81358139.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

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43

Branched-PE/i~PP Reactor Blends Prepared through Ethylene Gas-Phase Polymerization Catalyzed by a-Diimine Nickel Supported on iPP Particles Chunwen Guo, a Hong Fan,E* Bo-Geng Li, a Shiping Zhu b "State Key Laboratory of Polymer Reaction Engineering, Department of Chemical and Biochemical Engineering, Zhejiang University, Hangzhou 310027, China, e-mail: hfan(a)ziu. edu. en b Department of Chemical Engineering, McMaster University, Hamilton, L8S 4L7, Canada

Abstract Branched-PE/i-PP reactor blends that contain above 20 wt% of the branched PE were prepared through in-situ ethylene gas-phase polymerization catalyzed by a-diimine nickel catalysts ([ArN=C(CH3)-C(CH3)=NAr]NiCl2, Ar = 2,6dimethylphenyl) impregnated in iPP particles. The catalytic activities, the structure and properties of the in-situ blends were investigated and discussed. The activity results from the supported gas-phase polymerization were also compared to those from its unsupported slurry counterpart. 1. INTRODUCTION There are several ways to improve the low-temperature impact properties of iPP, such as introducing certain amount of EPR in iPP by mechanical blending or by in-situ (in-reactor) blending. Brookhart found that hyper branched or highly branched polyethylene (PE) could be produced from ethylene-only feedstock with a-diimine nickel or palladium catalysts [la] based on the "chain walking" mechanism proposed by Guan et al. [2]. Such PE materials are excellent candidates as rheological or impact resistance modifiers for making

246

C.Guoetal.

high impact PP (HIPP) [3], But it is not easy to disperse branched PE in iPP by simple mechanical mixing. Catalysts supporting is an effective approach for slurry or gas-phase polymerization processes. There are a few studies on the ethylene polymerization using supported a-diimine nickel or palladium catalysts [4-8]. In general, the activities of supported catalysts are lower than those of homogeneous polymerization, and polymer microstructure and properties are different, depending on support type, supporting method, and polymerization conditions. In these studies, various support systems have been adopted to impregnate the a-diimine nickel or palladium catalysts, such as S1O2 [5], MgCl2 [6] and nanotube (MCM-41 and MSF) [7] etc. However none of them used nonpolar polymer particles such as porous PP particles as support. In this way, an in-situ alloy of polymers can possibly be prepared. In this work, we made effort to use porous PP particles as support for adiimine nickel catalyst in ethylene gas polymerization. The catalyst activities of ethylene polymerization in i-PP particle are investigated. The structure and properties of the branched-PE/i-PP reactor blends are characterized. 2. EXPERIMENTAL All operations were performed with Schlenk techniques under a dry nitrogen atmosphere. a-Diimine Nickel catalysts ([ArN=C(CH3)-C(CH3)=NAr]MCl2, Ar = 2,6-dimethylphenyl) was synthesized according to literature [1]. MAO was purchased from J&K chemical company, A polymerization-grade ethylene gas was purified by passing it through CuO, ascarite, and 5A molecular sieves. Toluene and hexane were refluxed over potassium with benzophenone as indicator and distilled under nitrogen atmosphere prior to use. Porous iPP particles, 0.3-1.0 mm in diameter and 20% in porosity, were synthesized with TiCL(/MgCl2/SiO2 as the catalyst and AlEt3 as the co-catalyst. The iPP particles were eluted with hot heptane to eliminate the dissolved composition. The pretreated iPP particles were charged into a 250 ml flask with a magnetic stirrer. After vacuumed for 2 hours and purged with UHP Ni for five times, MAO hexane solution was injected into the flask that contains the iPP particles and mixed for 30 min. Hexane solution of catalyst was injected into the flask, and the iPP particles were impregnated with the catalyst for 30 min. The solvents were then vacuumed for 30 min. The flask was immersed into an oil bath with a pre-set temperature controlled at 5 °C. The ethylene gas was finally fed to the flask. When ethylene was charged to the flask, pale-brown iPP particles became blue, suggestion an activation of the catalyst. The ethylene gas-phase polymerization was carried out at ambient pressure for 60 min. The reaction was stopped by adding 10% acid ethanol. The produced

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247

polymer was filtered, washed with a large amount of ethanol, and dried under vacuum at 70 °C overnight. A differential scanning calorimetry (DSC) was conducted using a Perkin Elmer DSC-7 system at 10 °C/min. 13C NMR spectra of the polyethylene samples were recorded at 120 °C in 10-mm tubes with an Inova 300-MHz spectrometer. The samples were dissolved in o-dichlorbenzene/benzene-rfg to form 15 wt % solutions. 3. RESULTS AND DISCUSSION

3.1. Catalyst activity Table 1 summarizes the catalyst's activities in the supported gas-phase polymerization of ethylene. The activity increased with temperature with its highest value at 20 °C. The weight contents of polyethylene in the final product were about 20 wt% when the temperature was in the range of 20-~40 °C. Further increasing temperature decreased the catalyst activity. This trend was the same as unsupported slurry polymerization. However, the catalyst activity of the supported gas phase polymerization was much lower than the unsupported slurry counterpart at the same temperature. This activity reduction can be attributed to a hindering effect imposed by the PP particles. The catalyst impregnation in non-polar polymer particles is mainly based on physical adsorption. It was discovered that the sequence of catalyst and cocatalyst addition played an important role. When the porous iPP particles were first impregnated with the MAO solution, followed by the catalyst solution, the catalyst activity was higher than the reversed order of addition. This suggests that more active centers were generated by this way. Table 1. Catalyst activity, Tm and Tc of PE at different polymerization temperatures run

temp fC)

impregnation method

Tm

Te

(°C)

fC)

PEin

activity gas phase

(wt%)

(kgPE/mol.Ni.hr)

activity in slurry unsupported (kgPE/mol.M.hr)

1

10

MAO first

121

99

7.0

52.8

730.0 (t R 60min)[lb]

2

20

MAO first

121

100

22.4

202.9

610.0 (tR 60min) [lb]

3

20

Catalyst first

-

-

19.3

16B.2

1142.9 (tR30min)

4

30

MAO first

118

94

20.1

176.5

601.5 (t R 30min)[lb]

5

30

Catalyst first

-

-

6.6

49.9

6

40

MAO first

112

93

lg.9

163.5

7

50

MAO first

111

92

11.1

87.9

310(t R 60min)[lb]

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C. Guo et at

3.2. Polymer characterization The PE materials extracted from the product (run 3 in Table 1) contained mainly the CH3 branches based on the 13C-NMR spectrum (lb Fig. 1). The high peak intensity of CH2 means the PE synthesized inside the iPP particles had a low degree of branching, similar to linear low-density PE, Using the method for calculation [9], we found that the degree of branching of the branched PE was about 15 branches per 1000 C's. With the corresponding homogeneous catalyst, the branched PE obtained from the slurry polymerization at the same temperature had the degree of about 28 br/lOOOC. This suggests that the chainwalking feature in the gas-phase polymerization with a-diimine nickel catalysts impregnated in iPP particles was weakened due to the hindering effect. it.)

a,)

Figure 1 "C-NMR spectra (a) branched PE synthesized in slurry process (T = 20 °C); (b) the branched PE extracted from brPE/iPP (T = 20 °C) (run 2).

The DSC analysis was made to characterize the polymer structure and properties. In Fig. 2, the first scanning curve of the branched PE/iPP reactor blend (run 2) showed the original character of the in-situ formed PE inside iPP particles. There were two melting peaks at 121 °C and 162 °C, which correspond to the branched PE and i-PP respectively. The branched PE extracted with heptane from the PE/iPP product exhibited shoulders in a wide range of temperature 75 to 120 °C, suggesting it was actually consisted of PE molecules with various degrees of branching. The main melting peak occurred at 113 °C. The branched PE synthesized by slurry polymerization with the homogeneous catalyst consisted of at least three PE components with different branching degrees, which correspond three melting temperatures of 72, 99, 121 °C, respectively. As the PE thermal properties are related to its microstructure, the lower Tm for the main melting peak at 99 °C gave further evidence that the

43. Branched-PE/i-PP Reactor Blends through Gas-phase Polymerization

249

branched PE by the slurry process had a high level of branching. Increasing temperature in the gas-phase polymerization decreased the melting temperature of the branched PE. This suggests that high temperature favored the chain walking mechanism. — —

3232

brPE/iPP(Run2) brPE/iPP(Run 2) brPE(slurry process) process) brPE(slurry brPEextracted(Run2) brPE extracted(Run 2)

Heat flow endo up(mW)

30 30-

Q. 3

28 26 24 22

2020 1818 16 40

50 60 60 70 70 80 80 90 90 100 100 110 110 120 120 130 130 140 140 150 150 160 160 170 170 180 180 50 o

TemperatunefC) Temperature( C)

Figure 2 First DSC scanning curves of the branched PE synthesized in slurry process (T = 20 °C), the branched PE/iPP reactor blend, and the branched PE extracted from brPE/iPP (T = 20 °C) (run 2 ) 30 30-i 25 25-

-brPE/iPP(Run2) brPE/iPP(Run 2) o - brPE(slurry brPE(slurry process, process, 20 C)) - brPE brPE extracted(Run 2) 2)

Heat flow endo up(mW)

| 2 020H s 15H 15 10 105 50 0-5 -5-10 40

60

80

100 100

120 120

140 140

160

180

o

TemperaturefC) Temperature( C)

Figure 3 DSC cooling scanning curves for the branched PE/i-PP product (run 2), the extracted branched PE and the branched PE by slurry polymerization process.

250

C. Guo et al.

20

Heat flow endo up(mW)

o

Run 2, 20 C Run Run 4, 40oC Run Run 5, 50oC Run

18

16

14

12

10 50

60

70

80

90

100

110

120

130

o

Temperature( C))

Figure 4 Cooling scanning curves of the branched PE extracted from the branched PE/iPP reactor blends at different polymerization temperatures.

Fig. 3 shows the cooling behavior of the polymers. There existed two crystallization temperatures for the branched PE/i-PP reactor blends (Run 2): one is the Tc for iPP at about 110 °C, the other is for the branched PE at about 100 °C. This indicated that the in-situ synthesized branched PE was not uniformly dispersed in the iPP particle at a molecular level. Instead, it formed an independent phase inside the particle. The branched PE extracted with heptane showed two crystallization temperatures at about 91 °C and 96 °C, which corresponded to the two main components with different degrees of chain branching. Meanwhile, the TB of the branched PE obtained by the slurry process appeared to be lower, at 82.5 °C. There was another minor crystallization peak at 95 °C. The relative lower crystallization temperature Tc of PE indicated its higher degree of branching in microstructure. The crystallization exothermal curves of the extracted branched PE obtained at different polymerization temperatures were shown in Fig. 4. Two crystallization temperatures were found and appeared to move in the opposite directions when the gas-phase polymerization temperature was increased. The proportion of the exothermal area corresponding to the lower crystallization temperature increased and that corresponding to the higher crystallization temperature decreased for the extracted branched PE obtained at the polymerization temperature of 40 °C, when it was compared to that of 20 °C. This indicated more PE components that have higher levels of chain branching were formed at the higher polymerization temperature. For the case of 50 °C, the overall crystallization exothermal heat became smaller and the lower crystallization exothermal peak was not observed in the range tested.

43. Branched-PE/i-PP Reactor Blends through Gas-phase Polymerization With respect to the distribution of the branched PE materials inside the i-PP particles, the branched PE was favorably formed in the surface area of the iPP particle, but it was also formed to fill the inner pores through ethylene diffusion. This result was observed based on the preliminary morphological study of the branched PE/i-PP reactor blend. The materials distribution is closely related to the morphology of the porous particles as well as the method of catalyst impregnation. Further work in this regard is underway, 4. CONCLUSIONS The branched-PE/i-PP reactor blends that contain more than 20 wt% of the branched PE were prepared through an in-situ gas-phase polymerization of ethylene in iPP particles catalyzed by impregnated a-diimine nickel. The highest reaction activity was observed at the polymerization temperature of 20 °C. Due to the hindering effect inside the iPP particles, the reaction activity was lower than the slurry polymerization with the homogeneous catalyst. Based on the analysis of chain structure and thermal properties, the overall level of chain blanching of the formed PE in the iPP particle, which composed of several components with different microstructure, increased upon increasing polymerization temperature, but was obviously lower than the branched PE obtained from the slurry polymerization process. Acknowledgements This work was financially supported by the Special Fund for Major State Basic Research Projects (No.2005CB623804), the National Science Fund for Oversea Distinguished Young Scholars (No.20428605), and the National Science Fund (No.20476090). References [1] (a) L. K. Johnson, C. M. Killian, M. Brookhart, J. Am. Chem. Soc. 117 (1995) 6414. (b) F. Zhu, W. Xu, X. Liu, S. Lin, J. Appl. Poly. Sci. 84 (2002) 1123. [2] Z. Guan, P. M. Cotts, E. F. McCord, S. J. McLain, Science 283 (1999) 2059. [3] O. Vogl, J. Macromol. Sci., Pure Appl. Chem. A35 (1998) 1017 [4] (a) J. A. M. Canich, D. E. Gindelberger, P. T. Matsunaga, G. A. Vaughan, K. R Squire, WO 9748736. (b) A. M.Bennett, S. D. McLain, WO 9856832. (c) C. M. Killian, G. G. Lavoie, P. B. MacKenzie, L. S. Moody, WO 9962968. [5] (a) F. AlObaidi, Z. Ye, S. Zhu, Macromol. Chem. Phys. 204 (2003) 1653. (b) L. C. Simon, H. Patel, J. B. P. Soares, R. F. de Souza, Macromol. Chem. Phys. 202 (2001) 323.

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CGuoetaL

[6] J. R. Severn, J, C. Chadwick, Macromolecules 37 (2004) 6258. [7] Z. Ye, H. Alsyouri, S. Zhu, Y. S. Lin. Polymer, 44 (2003) 969. [8] P. Preishuber-Pflugl, M. Brookhart, Macromolecules 35 (2002) 6074. [9] T. Usami, S. Takayama, Polymer J. 16 (1984) 731.

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Kinetics of Propylene Bulk Polymerization with a Spherical Ziegler-Natta Catalyst Bogeng Li,a* Hong Fan,a Jijiang Hu,a Shiping Zhub "State Key Laboratory of Polymer Reaction Engineering, Department of Chemical and Biochemical Engineering, Zhejiang University, Hangzhou 310027, China, e-mail: hgli&xju. edu. en b Department of Chemical Engineering, McMaster University, Hamilton, L8S4L7, Canada

Abstract Experiments were carried out in a novel laboratory reactor with an on-line monitor and a control system to study the kinetics of bulk polymerization of propylene in both gas and liquid phases. Flory-Huggins equation was used to estimate the monomer concentration in the amorphous region of the polymer. The time evolution of polymerization rate under all conditions followed the same pattern, with a fast decay in the early stage of the polymerization and a relatively slow decay in the later stage. Two nth-order decay models were developed to describe the polymerization rates. Experimental data were used to estimate the model parameters. It was found that the apparent activation energies in both phases were similar to each other, while the decay order in the liquid phase was found to be 1.7 that was lower than that in the gas phase process. It implied that less thermal runaway was achieved in the liquid process. The model described the experimental results well. 1. INTRODUCTION To achieve high-impact polypropylene (PP) materials, one can mix PP materials with rubbery compound in an extruder. However, the compounding process is proven to be energy consuming. A more promising approach for making these multiphase materials is to produce them directly in the

254

B.Lietal.

polymerization reactors, which usually involves a multistage polymerization process [1-4]. As shown in Figure 1, propylene is introduced into spherical particles of a Ziegler-Natta catalyst supported on magnesium chloride. Spherical PP particles are prepared in the first stage of the process. A mixture of ethylene and propylene is then introduced into the PP particles to yield a second component that provides a soft phase to absorb mechanical energies from sudden shocks. The structure and morphology of PP particles are important factors that affect the catalysis and kinetics of ethylene-propylene polymerization in preparing the final alloy. The stage of propylene polymerization therefore plays a key role. The kinetics of propylene polymerization was investigated by a number of researchers in various solvents and in gas-phase at ambient pressure [5-16]. However, little work has been done to polymerize propylene at high pressure or in liquid phase due to the critical experimental conditions required. In our previous paper [17], we reported the kinetics of gas-phase polymerization at elevated pressures. In this work, we make effort to investigate the kinetics of the liquid-phase polymerization of propylene. We emphasize on the comparison and contrast of these two polymerization systems. It should be pointed out that the part of the gas-phase polymerization work initially appeared in Ref 17. The data are included here for the comparison purpose as well as for providing a complete set of the data in a single paper. The aim of this study is focused on the following two aspects: (1) kinetic study of gas-phase propylene polymerization with elevated pressure; (2) kinetic study of liquid-phase propylene polymerization. Propvlene

Ethylcnc Propylene

Catalyst particles

Porous PP pai tides

HP/KPR alloy

Flg.l. Synthesis of polyolefin alloy via multistage polymerization

44, Kinetics ofPmpylene Bulk Polymerization with a Ziegler-Natta Catalyst

255

2. EXPERIMENTAL The polymerization essays were carried out in a novel laboratory reactor system equipped with an on-line monitor and a controller (Figure 2). The detailed reactor setup was described in our previous work [17], The equipment consists of four parts. The first part is for the storage and purification of raw materials. The second part connects the feeding system of purified materials to the reactor. The third part includes an on-line monitor and a controller. In particular, the gas-phase composition controller is installed in the vent line of the reactor, which is achieved by the combination of a differential pressure volumetric flow meter (VFC) and a thermal mass flow meter (MFC) with a delay time of 0.01-3 s, faster than that with infra-red (IR) spectrum [18-20]. This system is especially useful to study the kinetics of binary gas-phase copolymerization of olefins, in which the compositions of the monomer feeds should be precisely controlled. The gas-phase polymerization of propylene was carried out in a semibateh mode with granular Teflon (polytetrafluoroethylene) served as a seed bed in the reactor. In contrast, the liquid-phase polymerization was in a batch mode. The catalyst was a commercial spherical TiCVMgCla Ziegler-Natta catalyst with triethylaluminium (TEA) as cocatalyst and diphenyldimethoxylsilicane (DDS) as the external donor to control the polymer stereoregularity. Both processes used the same catalyst system. The solvent used in the system was distilled with potassium. All the operations were done under an atmosphere of purified nitrogen since the catalyst system is extremely sensitive to impurities even at a trace amount. Filter MFC

H2 Filter MFC

N2

Filter MFC

C2H4

Vaccum Filter MFC

Filter

C3H6

Evaporator

Reactor

Regulator

VFC

MFC

Fig. 2. Vertical stirred bed reactor system for gas-phase polymerizations

Vent

B. Li et al.

256

3. RESULTS AND DISCUSSION 3.1. Estimate of Monomer Concentration The morphology of a single particle is often described by the multigrain model [21-25]. Upon an injection of catalyst, the monomer starts to diffuse into the catalyst particles and the catalytic centers are activated. As shown in Figures 3 and 4, the monomer needs to penetrate the amorphous region of a polymer film to reach a center as soon as the polymer film is formed. To determine the reaction rate at the active center, one needs to know the monomer concentration in the amorphous region of the film. polymer

*

*J

I

"

m M ihe urfkcc at i

Fig. 3. The simplified picture of polymer particle [25].

Fig. 4. Structure of micro polymer particle.

This concentration can be predicted by Henry's Law under low pressure: Cm=kP* (1) where Cm is the monomer concentration inside the polymer particle; k is the Henry constant, and P* the monomer pressure. The Henry constant can be calculated from the following equation [26]:

where Tc is the critical temperature. Flory-Huggins equation is applicable for high pressure [27, 28]:

44. Kinetics ofPropylene Bulk Polymerization with a Ziegler-Natta Catalyst

257

= In Fi where P* and P^1 are the partial and saturation vapor pressures of the monomer, respectively; Vt is the monomer volume fraction in the amorphous part of the particle, and % is the Flory-Huggins interaction parameter. The value of the Flory-Huggins interaction parameter can be calculated from the following equation [29]:

j=(1.13/P 8at )exp(0.345 P*)

(4)

The monomer concentration in the polymer can thus be estimated by:

c. = v,c,

(5)

where Q is the corresponding concentration of the liquid monomer. 3.2. Kinetic model We developed the following kinetic model in our previous paper [17]. According to this model, the polymerization rate can be described by the following equation:

X,=k,Cj?

(6)

with

where kp is the propagation rate constant, C* is the overall concentration of active centers, Ev is the activation energy for the apparent propagation reactions; and Tis the temperature. The catalyst decay is described by:

at with

kd=kdfieKT

(9)

where ka is the deactivation constant; n is the order of deactivation. E^d is the activation energy for the apparent deactivation reactions; and T is the temperature. Combining Eq 6 with Eq 8 gives:

258

B. Metal

00) D

If 11=1, it is

I

ft

ln(—^ R

- ) = kdt

(11)

plCm

Ifn>l,itis

( r

1

- ( ) " -)"-' ' = (« ( -1)-^M 1)^M

A linear regression of ln(Rp /Cmm) or (

(12) )""' versus t allows one to

R R llCC

p m

determine the decay order «. The standard deviation of the linear regression is defined as:

N

_

2

where (ypt^ are the data points, A is the intercept value, N is the number of the data points, K is the slope. The relative standard deviation is defined as: SD — i,mast

yi,minJf

where yiimm,yitmin,ti>mm,tiimin

— — \ i,max

(14)

i,minJ

are maximal and minimal values of y, and

tt respectively. When y=f(t) is a strictly increasing function, Eq. 14 can be simplified as:

RSD=^-

(is)

The value of n at the minimal RSD gives the decay order.

44. Kinetics ofPropylene Bulk Polymerization with a Ziegler-Natta Catalyst

259

3.3. Kinetics of gas-phase Propylene Pofymerizationfl7]

J.J.I. Effects of conditions on rate It is desirable to determine the catalyst efficiency since a trace level of impurities may totally deactivate active centers in an olefin polymerization. Catalyst residues in the feed line may also result in an underestimate of the catalyst activity (as shown in Fig.5). The cocatalyst also has an effect on the catalyst activity. There is an optimal cocatalyst/catalyst ratio under which the catalyst has the highest activity (as shown in Fig.6).

30

60

90

120

150

Massofthecatalyst/mg

Figure 5. Determination of the catalyst efficiency at 70 °C.

B. Li et al.

260

2500

500

100

150

200

AI/Ti ratio/moLmor

Figure 6. Effects of Al/Ti ratio on polymer yield at 70 °C

The effect of monomer concentration was investigated under 70 °C. As shown in Fig.7, the monomer pressure is in the range of 0.50~-'1.15MPa. The rate is proportional to the monomer concentration.

0.00

0.25

0.50

0.75

1.00

1.25

Monomer conccntration/niol.L-amorp

Figure 7 Mean reaction rate at 70 °C during One-hour polymerization.

3.3.2. Determination of the decay order of the active centers A typical experimental reaction rate curve is shown in Fig.8. As we can see a fast decay in the early stage followed a steady decay. The relative standard

44. Kinetics ofPropylene Bulk Polymerization with a Ziegler-Natta Catalyst

261

deviations (RSDs) were plotted against the decay order n for each experiment set as shown in Fig, 9, The decay order was determined to be 2.5 by the mean value of these RSDs as shown in Fig. 10. 1500 a 1200

experi merit Exponential

decay

0.6

0.9

0.3

fit

1.2

Time/h

Figure 8 Typical experimental reaction rate at 70 "C, 0.60 Mpa

0.20 Relative standard deviation

Run numbs H305A H309A H311A H313A * H315A e H319A H H321A

o e

0.16 0.12

V 4

*

H321A H308A H310A H312A H314A H316A H320A

0.08 0.04 0.00

1

2

3

4

5

Decay order n

Figure 9 Determination of the decay order of the active sites for each of the experiments.

262

B.Lietal

Mean relative standard deviation

0.15 0.12 0.09 0.06 0.03

1

2

3

4

5

Decay order n

Figure 10 Determination of the decay order of the active sites for all the experiments.

3.3.3. Estimate of the apparent activation energy and other rate constants

100000

-1

-1

Rp0 /L-amorp.gPP.gcat .hr .mol

-1

The rate constants were determined in Fig. 11-12, and the values of these constants were listed in Table 1 in detail.

10000

1000

100 10 2.85

2.90

2.95 3.00 3.05 -1 -1 1 T'/IOOO.K T /1000.K

3.10 3.10

Figure 11 Arrhenius plot of the initial reaction rate at 49—76 °C.

44, Kinetics ofPropylene Bulk Polymerization with a Ziegler-Natta Catalyst

263

2.85 2.90 2.95 3.00 3.05 3.10 T"1 /1000.K"1 Figure 12 Arrhenius plot of the deactivation constant k^/kp1'5 at 49~76 °C. Table 1. Constants of the Kinetic Model for Gas-Phase Propylene Polymerization Constants

Units

Values 2.5

kJ/mol

77.1

kJ/mol

51.8

gPP.L-amorp.gcat" .hr" .mol"

2.80x10 15

(goat/gpp) L 5 (mol/L-amorp) L5 hr 0 - 5

3.66x10',-15

3.3.4. Model test The model predictions and experimental data were plotted simultaneously, as shown in Fig. 13, the model describes the experiments reasonably well.

264

5. Li et al.

o.3

o.a

o.a

Time/hr

(b) at 65.2 °C, 0.595 MPa,

(a) at 76.2 °C, 0.808 MPa;

Figure 13 Comparison of experimental and simulated reaction rate

3.4. Kinetics of liquid-phase Propylene Polymerization 3.4.1. Polymerization rate The rate of liquid-phase polymerization was obtained by correlating the yield versus time data using Fig,14~15. 30

exper i rent ExpAssoc fi t

25-

J20 B5

I15" 1 1050

0.0

0.2

0.4

0.6

0.8

1.0

Time(h) Figure 14 Yield of the catalyst as a function of main polymerization time at 80 °C.

44. Kinetics ofPropylene Bulk Polymerization with a Ziegler-Natta Catalyst

265

20000 f 18000| 16000| 14000

I 12000| 10000-

I 8000-

^ eooort

40002000 0,0

0,2

0,4

0,6 0.

1,0

Figure 15 Instantaneous polymerization rate as a function of main polymerization time at 80 °C.

3.4.2. Determination of Decay Order The decay order is determined to be 1.7 (as shown in Fig. 16)

2

3

4

Decay order

Figure 16, Determination of the decay order of catalyst decay for all the experiments

3.4.3. Estimate of the apparent activation energy and other rate constants The rate constants were determined in Fig, 17-18, and the values of these constants were listed in Table 2 in detail.

266

B. Li et at.

ft 10 t*

2.8

2.9

3.0

rViooo.iT1 Figurel?. Arrhenius plot of the initial reaction rate at 50-80 °C

2.80 2.85 2.90 2.95 3.00 3.05 3.10 3.15 T"1 /1000.K"1 Figure l i . Arrhenius plot of the deactivation constant k^/kp

at 50~i0 °C.

Table 2. Constants of the Kinetic Model for Liquid-Phase Propylene Polymerization Constants

£„

Units

Values

i

1.7

kJ/mol

72.9

kJ/mol

48.7

gPP.L-amorp.gcat" .hr" .mol"

1.45x10 15

(gcat/gpp) °- 7 (moyL-amorp)0-7hr"0-3

1.34xlO":

44, Kinetics ofPropylene Bulk Polymerization with a Ziegler-Natta Catalyst

267

3,4.4. Model test

The model predictions and experimental data were plotted simultaneously, as shown in Fig. 19, the model describes the experiments well. o

2020

25 experiment -model model

Yield (kgPP/gCat.)

Yield gPP/gCa»t.) t.) Yiel i (k (kgPP/gC

25

15 15O —

1010 ^—-

55 0 00.0

0.2

0.6 0.4 Time (h)

0.8

experiment model

20 15 10 5 0

1.0

0.0

(a) at 60 °C

0.2

0.4 0.6 Time (h)

0.8

1.0

(b) at 70 °C

Figure 19. Comparison of experimental and simulated reaction rate.

3.5. Comparison of Gas-phase and Liquid-phase Polymerization Systems 3.5.1. Comparison of the catalyst composition Table 3, Comparison of the catalyst composition for gas- and liquid-phase propylene polymerization system Polymerization system

DQcat

Aim

tag

/moLmol -1

Gas-phase

50-120

150

7.5

Liquid-phase

20

720

36

Si/Ti /moLmol

-1

From the table we can find that there are differences in the catalyst composition between the two catalyst systems. J. 5.2. Comparison of the reaction rate The reaction rates of gas- and liquid-phase polymerization were compared in Fig. 20~21. From these figures we can see that the gas-phase polymerization rate is much lower than that of the liquid-phase counterpart. Theoretically, they

268

B. Li et al.

should be equal at the same temperature. This may suggest that the efficiency of the catalyst in the gas-phase be much lower than that in the liquid-phase. 14000

°

liquid-phase gas-phaie at 0.559 MPa

q12000B

0.0

0.3

0.9

1.2

Time(h)

Figure 20 Comparison of reaction rate for liquid and gas phase experiments at 70.0 °C.

0.0

0.2

0.4

0.6

0.8

1.0

Time(h}

Figure 21 Ratio of reaction rate for gas and liquid phase experiments at 70.0 °C.

3.5.3. Comparison of the decay orders and activation energies It was found that the apparent activation energies in both phases were similar to each other, while the decay order in the liquid phase was found to be 1.7, lower than that in the gas phase process. This may imply that less thermal runaway was achieved in the liquid process.

44. Kinetics of Propylene Bulk Polymerization with a Ziegler-Natta Catalyst

269

Table 4. Comparison of the decay orders and activation energies for gas- and liquid-phase propylene Polymerization system Polymerization system Gas-phase

« / ' 25

£p

Ed

/kJ.moP TTA

/klmol" 1 SL8

Liquid-phase

1.7

72.9

48.7

T

T

4. CONCLUSIONS The kinetic models of bulk propylene polymerization have been developed for both gas- and liquid-phase using a spherical Ziegler-Natta catalyst. A faster decay order was found in the gas-phase system, suggesting that thermal runaway may be more severe in the gas-phase process than in the liquid-phase. The differences in the reaction rates and in the catalyst compositions between gas- and liquid-phase polymerization systems suggest that the catalyst efficiency in the gas-phase be much lower than that in the liquid-phase due to a trace amount of impurities. Both models describe the experiments moderately well. Acknowledgement! This work was financially supported by the Special Fund for Major State Basic Research Projects (No.20G5CB623804), the National Science Fund for Oversea Distinguished Young Scholars (No.20428605), and the National Science Fund (No.20476090). References [1] P. Galli, J. C. Hayloek, Die Makrom. Chem. Macromol, Symp, 63 (1992) 19. [2] J. A. Debling, J. J. Zacca, W. H. Ray, Chem. Eng. Sci. 52 (1997) 1969. [3] P. Galli, G. Collina, P. Sgarzi, G. Baruzzi, E. Marchetti, J, Appl. Polym. Sci. 66(1997)1831. [4] G. Collina, T. Dall'oeco, M. Galimberti, E. Albizzati, L. Noristi, WO9611218. [5] H. G. Yuan, T. W. Taylor, K. Y. Choi, W. H. Ray, J. Appl. Polym. Sci. 27 (1982)1691 [6] J. C. W. Chien, C. I. Kuo, T. L. Ang, J. Polym. Sci.: Polym. Chem. 23 (1985) 723 [7] J. C. W. Chien, C. I. Kuo, J. Polym. Sci.: Polym. Chem. 23 (1985) 731.

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[8] J. C. W. Chien, C. I. Kuo, J. Polym. Sci.: Polym. Chem. 23 (1985) 761. [9] C. Dumas, C. C, Hsu, J. Appl, Polym. Sci. 37 (1989) 1625. [10] S. Cai, S. Xiao, Y. Liu, Chinese J. Catalysis, 12 (1991) 409. [11] X. Xia, B. Mao, Petrochem. Tech, 21 (1992) 440. [12] X. Xia, B. Mao, Petrochemical Technology, 21 (1992) 507. [13] 1. Kim, H. K. Choi, J. H. Kim, S. I. Woo, J. Polym. Sci.: Polym. Chem. 32 (1994)971 [14] I. Kim, H. K. Choi, J. H. Kim, S. I. Woo, J. Appl. Polym. Sci. 52 (1994) 1739. [15] J. Xu, L. Feng, S. Yang, Petrochem. Tech. 26 (1997) 581. [16] V. Mates, N. A. G. Mattes, J. C. Pinto, J. Appl. Polym. Sci. 79 (2001) 2076. [17] J. Hu, H. Fan, Z, Bu, B. Li, Journal of Chemical Industry and Engineering (China) 57 (2006) 429 [18] G. C. Han-Adebekun, J. A. Debling, W. H. Ray, J. Appl. Polym. Sci. 64 (1997) 373 [19] J. Hu, H. Fan, Z. Bu, B. Li5 Proceedings of 1st Chinese National Chemical and Biochemical Engineering Annual Meeting, Nanjing, China, (2004) 349. [20] B. Li, H. Fan, J. Hu, Z. Bu, J. Zhang, CN 1657543A. [21] M. Ferrero, M. G. Chiovetta, Polym. Eng. Sci. 27 (1987) 1436. [22] M. Ferrero, M. G. Chiovetta, Polym. Eng. Sci. 27 (1987) 1448 [23] R. A. Hutchinson, C. M. Chen, W. H. Ray, J. Appl. Polym. Sci. 44 (1992) 1389 [24] J. A. Debling, W. H. Ray, Indus, and Eng. Chem. Research, 34 (1995) 3466 [25] J. Kosek, Z. Grof, A. Novak, F. Stepanek, M. Marek, Chem. Eng. Sci. 56 (2001)3951 [26] S. A. Stern, J. T. Mulhaupt, P. J. Garies, AICHE J, 15 (1969) 64. [27] J. Samson, B. Middelkoop, G. Weickert, K. Westerterp, AICHE J, 45 (1999)1548. [28] R. A. Hutchinson, W. H. Ray, J. Appl. Polym. Sci. 14(1990) 51 [29] Y. Banat, U. P.Veera, G.Weickert, Proceedings of 2nd ECOREP, Lyon, France, July (2002)1.

Progress in Olefin Polymerization Catalysts and Polyolefin Polyolefin Materials T. Shiono, K. Nomura and M. Terano (Editors) © 2006 Elsevier B.V. All rights reserved.

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45

Effect of a-Olefins on Copolymerization of Ethylene and a-Olefin with [*-BuNSiMe2Flu]TiMe2 Catalyst Nawaporn mtaragamjona, Takeshi Shionob*, Bunjerd Jongsomjif** Piyasan Praserthdam8* "Center of Excellence on Catalysis and Catalytic Reaction Engineering Department of Chemical Engineering, Faculty of Engineering Chulalomgkam University, Bangkok 10330 Thailand ^Department of Applied Chemistry, Graduate School of Engineering, Hiroshima University, 1-4-1 Kagamiyama, Higashi-Hiroshima, 739-8527, JAPAN.

Abstract The effect of a-olefm was observed in ethylene/a-olefin copolymerization toward [?-BuNSiMeaFlu]TiMe2 catalyst with MMAO. Three kinds of a-olefm monomers were chosen for the present study. Activity, polymer microstrueture, thermal properties, molecular weight and molecular weight distribution of polymers were investigated. Our results revealed that the activity of polymerization was strongly dependent on the a-olefins employed. Thus, the polymerization behavior can be altered with the a-olefins used during polymerization. It indicated that the crystallinity of polyethylene was broken by the large amounts of a-olefin insertion on ethylene and a-olefin copolymer. 1. INTRODUCTION From the industrial point of view, linear low-density polyethylene (LLDPE) is produced in gas, solution and high pressure processes. The density of polyethylene is an important variable that we use to control polymer properties. Density of polyethylene can be controlled in many ways, especially, the level and distribution of branching. The catalytic polymerization of ethylene with «olefins is a typical way of introducing short-chain branching in polyethylene

272

JV. Intaragamjan et al,

backbone. Nowadays, new generation of polymerization catalysts i.e. metallocene and late transition metal catalysts, can control the amount of aolefin insertion into polyethylene with uniform and homogeneous sequence and composition distributions. With the difference of comonomer composition and its distribution, it can cause significant changes in polymer properties. These included differences in glass transition, melting temperatures, melt viscosity, the mechanical and optical properties [1-7]. As a matter of fact, we can use the ethylene/a-olefm in the wide range of applications. In the present paper, we are communicating the results of polymerization regarding to the a-olefin monomer in ethylene/oc-olefin polymerization behaviors. Polymerization proceeded with [t-BuNSiMe2Flu]TiMe2 and modified-methylaluminoxane (MMAO) system using heptane as the solvent medium. Polymer properties and polymer microstructure were also investigated to suggest the interpretation of comonomer effect on the copolymer composition and comonomer distribution. 2. EXPERIMENTAL Materials; All manipulations were carried out under an argon atmosphere using standard Schlenk techniques. All solvents were refluxed with sodium/benzophenone or calcium hydride and distilled before use. The complex was prepared according to the method reported previously [8]. Polymerization Procedure; Ethylene/a-olefm copolymerizations were carried out in a 100-ml semi-batch stainless steel autoclave reactor equipped with a magnetic stirrer. Heptane was introduced to reactor followed by the addition of the desired amount of MMAO. The catalyst was added to the reactor in a glove box. The reactor was then immersed in liquid nitrogen to freeze the solution and evacuated to remove argon. The a-olefin was added to the freezed reactor equipped with Schlenk line to keep system in argon atmosphere. After that, the reactor was heated to the desired polymerization temperature. Feeding ethylene started the reaction. The pressure in the reactor was kept at 50 psi by a continuous ethylene feed. Polymerizations were conducted on the certain time and terminated with acidic methanol. The polymer obtained was precipitated in acidic methanol, filtered, adequately washed with methanol, and finally dried in the atmospheric pressure for 3 days to ensure for solvent evaporation. Analytical Procedures; Molecular weights and molecular weight distributions of polyethylene obtained were determined by gel permeation chromatography (GPC) with a Waters 150CV at 135 °C using 1,,2,4-trichlorobenzene as a solvent. The 13C NMR spectra of the polyethylene were measured at 70 "C on a JEOL GX 500 spectrometer operated at 125.65 MHz in the pulse Fourier-transform mode. The pulse angle was 90° and about 5000 scans were accumulated in pulse

45. Effect ofa-Olefin on Copolymerization with [t-BuNSiMe3Flu]TiMe2 Catalyst

273

repetition of 4.0 s. Sample solutions were prepared in ehloroform-a?i up to 10 wt-%. Differential scanning calorimetry (DSC) curves of the samples were recorded on a Perkin-Elmer DSC P7 under nitrogen with a heating rate of 10 "C/min. 3. RESULTS AND DISCUSSION Ethylene/a-olefin copolymerization was conducted at 70 °C with various aolefin types, of which results are summarized in Table 1. The copolymerization of ethylene/a-olefin gave the highest activity when 1-octene was employed. From this evident, it should be noted that the active species of ion pair can be affected from the second monomer in polymerization. In this case the proper geometry and steric of 1-octene can generate the highest activity in ethylene/aolefin polymerization. Again, from Table 1, we found that the molecular weight of polymer was reduced when the copolymerization was conducted. This was because the chain transfer of polymer occurred after the a-olefin insertion unit during copolymerization. Moreover, with the higher a-olefin monomer, we obtained the higher molecular weight of copolymer. Table 1 Results of ethylene/a-olefin copolymerization3 Polymer

Yield (g)

Activity"

M n (10 4 ) 6

MWff

E°

0.75 3,08

1000 2460

4.2 2.6

3.9 2,2

3.52

2g20

3.6

2.0

2.31

1840

3.6

2.1

EH EO ED

7? 134

99

'Polymerization conditions: Ti = 5 (xmol, Al/Ti = 1000, 50 psi of ethylene pressure, polymerization temperature = 70 °C, bActivity = kg(polymer) mor'fTi) hr"1. cNumber of average molecular weight and molecular weight distributions were measured by GPC analysis using poly styrene as reference. d Measured by DSC (°C) "Using Ti = 3 junol.

A quantitative analysis of triad distribution for all copolymer samples was performed by 13C NMR. The assignments of the spectra their analysis were based on those of ethylene/1-hexene copolymer [9]. The triad distribution and product reactivity ratio of monomer are shown in Table 2. It should be noted that the a-olefin incorporation in the main chain of copolymer apparently decreased with the larger a-olefin monomer applied. The next focus was on the copolymer structure. The product of monomer reactivity ratios increased from 1.1 with 1-hexene to 2.4 with 1-decene according to the size of a-olefin, which indicates that the comonomer distribution in the

274

N. Intaragamjon et al.

copolymer was changed from random to blocky by the size of a-olefin comonamer. Table 2 Microstrueture and comonomer content of the copolymers Polymer

ccc

ECC

ECE

EEE

CEC

EEC

%E

%C

We

EH

0.097

0.243

0.124

0.203

0.137

0.196

54

46

1.14

EO

0.064

0.136

0.119

0.362

0.086

0.233

68

32

1.67

ED

0.025

0.106

0.096

0.558

0.064

0.150

77

23

2.36

E and C denote ethylene and comonomer (H = hexene, O = octene and D = decene), respectively.

4. CONCLUSIONS Comonomer effects were investigated in the copolymerization of ethylene and a-olefin with the [/-BuNSiMe2Flu]TiMe2MMAO catalyst. The size of the aolefin used as a comonomer was found to affect the copolymerization ability of the catalytic system, which was probably caused by the a-olefin inserted at the propagation chain end. Acknowledgments We give the grateful thanks to the Thailand Research Fund (TRF), The Thailand Japan Technology Transfer Project (TJTTP), and the Royal Golden Jubilee program scholarship. References [1] S. Bensason, J. Miniek, A. Moet, S. Chum, A. Hiltner, E. Baer, J. Polym. Sci., PartB: Polym. Phys. 34 (1996) 1301. [2] DJR, Burfield, Macromolecules 20 (1987) 3020. [3] R.G Alamo, L. Mandelkern, Thermochim. Acta 238 (1994) 155. [4] A. Alizadeh, L. Richardson, J. Xu, S. McCartney, H. Marand, Macromolecules 32 (1999) 6221. [5] D. Mader, Y. Thomann, J. Suhm, R. Mulhaupt, J. Appl polym. Sci. 74 (1999) 838. [6] A.G. Simanke, G.B. Galland, R.B. Neto, R. Quijada, R.S. Mauler, J. Appl. Polym. Sci. 74(1999)1194. [7] X.R. Xu, J.T. Xu, L.X. Feng, W. Chen, J. Appl. Polym. Sci. 77 (2000) 1709 [8] H. Hagihara, T. Shiono, T. Ikeda, Macromolecules 31 (1998) 3184. [9] James C. Randall, J. Macromol. Sci., Macromol, Chem, Phys. C29 (1989) 201.

Author Index Asuka, K. Babkina, O. N. Ban, H. T, Bravaya, N. M. Cai, Z. Chukanova, O. N. Dong, Q. Duan, Y-Q, Eisen, M. S. Faingol'd, E. E. Fan,H. Fan,Z. Fang,Y. Fu,Z, Fujita, T. Fujiwara, A. Guo, C. Hagihara, H. Hasebe, K. Horikawa, K. Horikosi, T. Hou, J. Hou, Z. Hu,J, Ikeda, T. Ishihara, T. Itagaki, K.

229,237 77 197 77 47,189 77 25 113 105 77 245,253 25 225 25 159 43 245 197 43 205 13 209 95 253 241 197 179

Jie, S. Jongsomjit, B Jung, M.-S. Kaneko, H. Kang, N. Kashiwa, N. Kawahara, N Kawamoto, N Kawamura, T. Kim, C. Kitiyanan, B. Kouzai, I. Kuwabara, J, Lee, D. W. Lee, D.-H Lee, H. Y. Lee, I.-M. Lee, Y. R. Li, B.-G. Li,N Li, X.-F. Li, Y.-S. Lisovskii, A. Liu,B. Luo, Y. Lyoo, Y. S. 275

87,209 271 53 1 31 1 1 13 229 59 213 237 135 59 53, 69,185 185 59 69 245,253 25 113 113 105 129,219,225, 229,237 95 69

276 Author Index Maeda, N. Maeyama, K. Matsugi, T. Matsumae, T. Matsuo, T. Michiue, K. Mitani, M. Miyamoto, K. Monrabal, B. Nakano, H. Nakayama, Y. Intaragamjon, N Negishi, Y. Nishii, K. Nishimura, N. Nitta, K. Noh, S. K. Nomura, K. Nomura, K. Nozaki, T. Okada, M. Onda, M. Osakada, K. Panin, A. N. Park, S. Praserthdam, P. Qin, H. Ryabenko, A. G. Sagae, T. Saito, J. Sanginov, E. A. Saratovskikh, S. L. Shiga, A.

165 193,205 1 241 1 159 159 43 35 19 47,165,171, 189 271 13 241 193 229,237 53, 69,185 13 123,147,175, 179,213 43 171 159 135,201 77 201 271 233 77 7 1 77 77 219

Shiono, T. Su,Z. Sudhakar, P. Suehiro, K. Sugano, T. Sumino, K, Sun, W.-H. Sundararajan, G Sung, J.-K. Takahashi, T. Takeuchi, D. Tayano, T. Terano, M. Tobita, E. Toyota, A. Uchino, H, Ushakov, E. N. Volkis, V. Wang, D. Wang, W. Wang, X. Watanabe, H. Wu,B. Wu,J. Xia,W. Xu,D. Xu,J. Xu,Y, Yamada, J. Yamaguchi, M. Yang, M. Yokota, H. Yoon, K.-B.

47,165,171, 189,197,241,271 35 153 7 19 229

87,141,209 153 53 19

135,201 19

7,13, 129, 219,225,229,237 7,13 193,205 19 77 105 31 123 25 43 141 31

129,225 31 25 31

123,175 229 233 13 53,185

Author Index 277 Zhang, H. Zhang, S. Zhang, W. Zhang, W. Zhang, X. Zhao,Y. Zhou, D. Zhu, S.

147 87,233 87 141,209 31 31 225 245, 253

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Subject Index polyethylene 173 ethylene/norbornene copolymer 187 cobalt 141,144,145 cocatalyst effect of 28,126 comonomer effect 95,100,274 eompatibilizer 233,235 composite polyethylene/clay 234,236 polyolefin/clay 235 polypropylene/SiOi 229,238 composition distribution 9,25,27,35, 36,272 controlled radical polymerization 1,4 copolymer ethylene 31 ethylene/1-decene 273 ethylene/1-hexene 273 ethylene/1-octene 273 ethylene/norbornene derivative 53 ethylene/propylene 25,27 ethylene/vinyl acetate 31 organic/inorganic 53 thermal property 63 thermal stability 64 copolymerization ethylene 55 ethylene/1 -hexene 46,95,99,213, 216 ethylene/2-methyl-l-pentene 179 ethylene/a-olefm 271,273 ethylene/cycloolefin 186 ethylene/norbomene 185 ethylene/propylene 19,23 ethylene/styrene 147,149,151 ethylene/tetracyclododecene 185

activation energy 256,262,268 antioxidant 11,13,15,16 (arylimido)(ketimide)vanadium 125, 175 (arylimido)vanadium dichloride 133

B bimetallic Zr complex 1,3-butadiene

135,137,138 197

Cj-symmetry 108 Cj -symmetry 153 chain migration 51,191 chain transfer 45, 83,98,116,117,139, 157,183,199,241,243,273 chain walk 174,203,248,249 chemical composition distribution 35 chiral organo-siloxane ligand 225,227 chromic acid 219, 221,223 chromium trioxide 129 clay acid strength of 18,20,23 support-activator 10 modified 233,235,236 13 CNMR wax 93 ethylene/1-hexeneeopolymer 100 polynorbornene 120 poly(methylene-1,3-cyclopentane) 139 279

280 Subject Index norbornene/norbornene derivative 206 norbomene/styrene derivative 194 197,198 propylene/1,3-butadiene styrene derivative 193 crystallization analysis fraetionation 35,38 (CRYSTAF) 50,52 Cs-symmetric cyclization polymerization 202,203 cyclopolymerization 201,202 1,5-hexadiene 135,138

D decay model decay order

253 253,258,260, 261,265,

density functional theory (DFT) 130,131, 132,223 deuterated propylene deuterium-hydrogen exchange diethylaluminum chloride diethylaluminum hydride a-diimine nickel diisobutylaluminurn hydride

129, 110 111 126 199 245 199

I in-reactor alloy 25 iron 87, 88, 89,90,93, 141,142,145, 146 isopropylidene diallylmalonate 201, 202,203

K P-ketoimine kinetic curve kinetic model

E enantiomorphic site enantioselectivity epimerization

95,96, 97,100 half-sandwich 147,213,216 half-titanocene 69,71,73,74 dinuclear immobilized 213 180,183 nonbridged 214 polymer-supported 256 Henry constant 53 hybrid eopolymer 156,172,174 P-hydride elimination hydrogenation 45 P-hydrogen elimination 98,107,183 hydrogen addition of 25 30 effect of

61 226,227,228 257,269

51,191 51 110

Flory-Huggins interaction parameter 257 FTIR ethylene copolymers 31, 33,34

Lewis base promoting effect of 82 ligand effects 71,135,147,179 living polymerization 50, 52, 189,191, 192,241,243 long chain branch 171,173 low-molecular-weight wax

90, 93

G 100,159,163 205, 206,207

group 4 metal Grubbs catalyst

H hafnocene

77, 79, 83

M macroinitiator 1,2, 3 metallocene 10,11,21,23,39, 55, 73, 75, 85, 137,186 cationization 22 methylaluminoxane (MAO) 53, 65, 87,

Subject Index 281 90,108,133,135,148,153,156, 159,162,163,165,168,169,179, 181,183,192,193,194,195,196, 197,209,216,230,238,247 modified (MMAO) 47,49, 50,51, 53, 55, 58,61, 65,67, 70, 81,113, 115,120,169,170,186,189,190, 191, 197,198, 200, 241, 243, 244, 271,274 montmorillonite 19,20,235 morphology 210,212,251,256 polypropylene 10,254 clay 10 control 10 polymer particle 209 polymer 229 spherulite 238

N nanoeomposite 235,239 palypropylene/SiOz 229,231,237, 240 nickel 59, 67,113,115,116,117,119, 120,121,141,142,145,146,171, 174,193,194, 196,209, 212,245, 248,251 niobium 165,167,168,169

o 135,137,219 olefin metathesis ollgomerization ethylene 87, 90, 92, 93,141,143, 146 organic/inorganic hybrid 53

paired interacting orbitals (PIO) 129,130,131,132, 133,134, 219,220,221,222,223 palladium 59, 61, 67, 141, 143,146, 201,202 9,11,17 pelletizing process Phillips catalyst 129,134, 219, 223,

225,228 photo-oxidation 233,235 photo-stability 229 photo-stabilization 235 poly(styrene-eo-hydroxystyrene) 213, 214 polyethylene 72 crystallization analysis fractionation 38 polymerization 1-hexene 95, 97,153, 154 2-hydroxyethyl methacrylate 1 bulk 14,253 ethylene 19,45,59,61,123,125, 126, 135, 137, 141, 143,144, 145, 157, 168, 171, 172, 213,216, 225, 247 gas-phase 245,247,248,249,250, 251,254,259,267,268,269 kinetics 225 liquid-phase 254,255,264,267, 268,269 norbornene 61,113,115,119,209 olefin 219 propylene (propene) 23,47,49, 52, 77, 79, 82, 83, 105, 106, 135,138, 140,189,190,191,192,241,242, 243,244,254,259,264,267,269 styrene 74, 99,147,149,157,159, 161,163,216,217 syndiospecific 50,147,149,161, 216,217 polymer-supported catalyst 215, 216 polymorphism of ethylene copolymers 36 polynorbornene 13 CNMR 120 glass transition temperature 120 polypropylene crystallization analysis fractionation 39 elastomeric 106,107 injection molding 8 isotactic 135,138 macroinltiator 1,3 powder stability 13,14

282 Subject Index process 7 spherulite 237,238 surface 4 syndiotactic 189,191,192 polystyrene syndiotactic 69,71,73, 74,75,149, 213 post-polymerization 47, 50, 189,191 preactivation 77,79, 80, 81 prepolymerization 19,22,24 pseudo-Cj -symmetry 153

R radical scavenger 205 radical scavenging activity 205,207 rate constant 257,262,265 reactor blend 245,248,250,251 refractive index 185 ring-opening metathesis polymerization norbornene 165,169,175,176 norbornene derivatives 205, 206,

192,242 syndiotactic pentad

191

tantalum 165,167,168,169 Tebbe reagent 43,45,46 Temperature Rising Elution Fractionation (TREF) 37, 38, 39,40, 41 titanium 65, 71, 74,75,105, 106,108, 153,154,155,156,157,182,215,

216,217,241,244 titanium benzamidinate complex 105 triisobuiylaluminum 19,22,23,24,28, 77,79,80,81,82,83,84,85 tris(pentafluorophenylborane) 171

U UV-vis

19,21,22,23, 80, 81,188

vanadium 123,125,127,175,176,178 scandium bis(alkyl) complex 95, 97 Schulz-Flory 90,145,146 short chain branch 171,173,225 silsequioxane 53 Simple Plastic Manufacturing 7 SiOa nanoparticle 230, 231 spherical MgCl2 209,210,211,212 stabilizer 7,11 stereoblock 78,84 stereoerror 110,111 stereoseleetlvity 78,85 supported catalyst 25,30,210,211, 212,214,215,216, syndiospecificity 51, 52, 70,190,191,

X-ray erystallography67, 141,142, 167 X-ray diffraction analysis 87,90

Ziegler catalyst 13 Ziegler-Natta catalyst 9, 10,254,269 zirconium 21,153, 154, 157,197 zirconocene 52, 77, 80, 81, 82, 135 isospecific 197 syndiospecific 83

Progress in Olefin Polymerization Catalysts and Polyolefin Materials: Proceedings of the First Asian Polyolefin Workshop, Nara, Japan, December

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