Vinylcyclohexane (VCH) was copolymerized with ethene and propene using methylaluminoxane-activated metallocene catalysts. The catalyst precursor for the ethene copolymerization was rac-ethylenebis(indenyl)ZrCl 2 (1). Propene copolymerizations were further studied with C s -symmetric isopropylidene(cyclopentadienyl)(fluorenyl)ZrCl 2 (2), C 1 -symmetric ethylene(1-indenyl-2-phenyl-2-fluorenyl)ZrCl 2 (3), and \meso"-dimethylsilyl[3-benzylindenyl)(2-methylbenz[e]indenyl)]ZrCl 2 (4). Catalyst 1 produced a random ethene-VCH copolymer with very high activity and moderate VCH incorporation. The highest comonomer content in the copolymer was 3.5 mol %. Catalysts 1 and 4 produced poly(propene-co-vinylcyclohexane) with moderate to good activities [up to 4900 and 15,400 kg of polymer/(mol of catalyst  h) for 1 and 4, respectively] under similar reaction conditions but with fairly low comonomer contents (up to 1.0 and 2.0% for 1 and 4, respectively). Catalysts 2 and 3, both bearing a fluorenyl moiety, gave propene-VCH copolymers with only negligible amounts of the comonomer. The homopolymerization of VCH was performed with 1 as a reference, and low-molar-mass isotactic polyvinylcyclohexane with a low activity was obtained. V V C 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: [6569][6570][6571][6572][6573][6574] 2006
A series of benzyl-substituted, dual-site ansa-metallocenes were synthesized and characterized. Their isolated rac-and meso-diastereomers were studied in propene polymerization after methylaluminoxane or borate activation. Catalysts' polymerization behavior were investigated in various polymerization conditions, and produced polypropenes (PPs) were characterized with NMR, GPC, and DSC. The rac-and meso-diastereomers of these unsymmetric catalysts bearing a SiMe 2 bridge produced PP with similar activity, tacticity, and molar mass. According to quantum chemical calculations, the benzyl group in the catalysts can rotate, having significant energy minima. The reason that the diastereomers produce PP with similar molar mass is linked to these local energy minima and is further discussed.
The dual-site zirconocene dichlorides rac-
and meso-SiMe2(3-benzylindenyl)(indenyl)ZrCl2 have
been synthesized and used, after a methylaluminoxane
activation, in propene polymerization. These diastereomers produce isotactic polypropenes with similar microstructures and molar masses under equivalent polymerization conditions.
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