Highly active ethylene polymerization and copolymerization with norbornene using bis(imino‐indolide) titanium dichloride–MAO system |
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Authors: | Weiwei Zuo Wen‐Hua Sun Shu Zhang Peng Hao Akinobu Shiga |
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Institution: | 1. Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China;2. Key Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, ChinaKey Laboratory of Engineering Plastics and Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, China;3. LUMMOX Research Laboratory, Tsukuba, Ibaraki 305‐0032, Japan |
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Abstract: | A catalytic system of new titanium complexes with methylaluminoxane (MAO) was found to effectively polymerize ethylene for high molecular weight polyethylene as well as highly active copolymerization of ethylene and norbornene. The bis (imino‐indolide)titanium dichlorides (L2TiCl2, 1 – 5 ), were prepared by the reaction of N‐((3‐chloro‐1H‐indol‐2‐yl)methylene)benzenamines with TiCl4, and characterized by elemental analysis, 1H and 13C NMR spectroscopy. The solid‐state structures of 1 and 4 were determined by X‐ray diffraction analysis to reveal the six‐coordinated distorted octahedral geometry around the titanium atom with a pair of chlorides and ligands in cis‐forms. Upon activation by MAO, the complexes showed high activity for homopolymerization of ethylene and copolymerization of ethylene and norbornene. A positive “comonomer effect” was observed for copolymerization of ethylene and norbornene. Both experimental observations and paired interaction orbital (PIO) calculations indicated that the titanium complexes with electron‐withdrawing groups in ligands performed higher catalytic activities than those possessing electron‐donating groups. Relying on different complexes and reaction conditions, the resultant polyethylenes had the molecular weights Mw in the range of 200–2800 kg/mol. The influences on both catalytic activity and polyethylene molecular weights have been carefully checked with the nature of complexes and reaction conditions. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 3415–3430, 2007 |
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Keywords: | addition polymerization cationic polymerization copolymerization ethylene polymerization imino‐indolide norbornene polyethylene (PE) titanium |
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