Efficient Synthesis of Functionalized Polyolefin by Incorporation of 4-Vinylcyclohexene in Ethylene Copolymerization Using Half-Titanocene Catalysts

Copolymerizations of ethylene with vinylcyclohexene (VCHen) by using Cp'TiCl2(X) [X = O-2,6-(Pr2C6H3)-Pr-i, Cp' = Cp* (1); X = N=(CBu2)-Bu-t, Cp' = Cp* (2) and Cp (3)] catalyst systems with MAO have been explored. The copolymerizations proceeded via. vinyl addition/insertion affording high molecular weight copolymers containing cyclohexenyl side chains (with uniform compositions as well as with unimodal molecular weight distributions) accompanied with certain degree of side reaction (intramolecular cyclization after VCHen insertion). Degree of the side reaction (cyclization) was dependent upon the catalyst employed, polymerization temperature, but was not affected by the time course, the Al/Ti molar ratios. The Cp-ketimide analogue (3) showed the best catalyst performance in terms of both the catalytic activity and the selectivity (lowest degree of the subsequent intramolecular cyclization) in the copolymerization. Quantitative epoxidation of the olefinic double bonds in the resultant copolymer has been achieved by using m-chloroperbenzoic acid under mild conditions; a facile, precise synthesis of functionalized polyolefin has. thus been demonstrated by adopting this approach.