CATIONIC HOMOPOLYMERIZATION OF ISOBUTYL VINYL ETHER AND SEQUENTIAL BLOCK COPOLYMERIZATION OF ISOBUTYLENE WITH ISOBUTYL VINYL ETHER - SYNTHESIS AND MECHANISTIC STUDIES

The living polymerization of isobutyl vinyl ether (IBVE) and sequentia l block copolymerization of isobutylene (IB) with IBVE have been achie ved using TiCl4 coinitiator in methyl chloride/ hexanes solvent mixtur es in the -80 to -40 degrees C temperature range. Poly(IB-b-IBVE) with similar to 100% blocking efficiency has been synthesized for the firs t time. Close to 100% initiator efficiencies as well as 100% crossover efficiencies were obtained with 2,4,4-trimethyl-2-chloro-pentane (TMP Cl) and PIBCl, respectively. The procedure involved capping with 1,1-d iphenylethylene, followed by the addition of nBu(4)NCl to reduce the c oncentration of free, uncomplexed TiCl4 to [TiCl4](free) < [chain end] before the addition of IBVE. Mechanistic studies indicated that the p resence of common ion salt is not necessary, and that living polymeriz ation of IBVE and sequential block. copolymerization of IB with IBVE c an also be accomplished in its absence when [TiCl4] ( [chain end]. It is proposed that under these conditions the gegenion is TiCl5-, a much stronger nucleophile compared to the Ti2Cl9- dimeric gegenion which d ominates at [TiCl4](free)/[chain end] greater than or equal to 2.