Trialkylaluminum-Free Modified Methylaluminoxane as a Cocatalyst for Living Polymerization of Olefins
This article reviews living polymerization of olefins with several dimethyltitanium complexes by the use of trialkylaluminum-free modified methylaluminoxane (dMMAO) as a cocatalyst. The excellent solubility of dMMAO allows living coordination polymerization of olefins in aliphatic hydrocarbons. A chelating diamidodimethyltitanium complex (1) conducted living polymerization of propene in heptane at 0°C to produce atactic polymer. Metal oxide-supported dMMAO was also effective as a cocatalyst for the controlled polymerization of propene with 1, where the propagation rate and the molecular weight distribution of the produced polymer were dependent on the metal oxide used. ansa-Dimethysilylene(fluorenyl)(tert-butylamido)dimethyltitanium (2) activated by dMMAO conducted living polymerization of propene at 0°C in chlorobenzene, toluene and heptane. The propagation rate and the syndiotactic(syn)-specificity of the catalyst were dependent on the solvent as follows: propagation rate, chlorobenzene > toluene > heptane; syn-specificity, chlorobenzene < toluene < heptane. The propagation rate and the syn-specificity were also dependent on the substituent on the fluorenyl ligand of 2, and a highly active and syn-specific living polymerization was achieved by the use of a 3,6-di-tert-butyl substituted complex (4). Complex 2 and its derivatives such as 4 activated by dMMAO also conducted living homo- and copolymerization of norbornene and 1-alkene in toluene, which afforded a variety of tailor-made polyolefins composed of norbornene and 1-alkene.
Keywords1-Alkene Living polymerization Modified methylaluminoxane Norbornene Propene Single-site catalyst Supported catalyst
The author acknowledges Tosoh Finechem Co. for donating cocatalysts.
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