Novel substituted epoxide initiators for the carbocationic polymerization of isobutylene

This article presents the first detailed account of the discovery that subs tituted epoxides can initiate the carbocationic polymerization of isobutyle ne. alpha-Methyl- styrene epoxide (MSE), 2,4,4-trimethyl-pentyl-epoxide-1,2 (TMPO-1), 2, 4,4-trimethyl-pentyl-epoxide-2,3 (TMPO-2), and hexaepoxi squa lene (HES) initiated isobutylene polymerization in conjunction with TiCl4. MSE, TMPO-2, and HES initiated living polymerizations. A competitive reacti on mechanism is proposed for the initiation and propagation. According to t he proposed mechanism, initiator efficiency is defined by the competition b etween the S(N)1 and S(N)2 reaction paths. A controlled initiation with ext ernal epoxides such as MSE should yield a primary hydroxyl head group and a tert-chloride end-group. The presence of tert-chloride end-groups was veri fied by NMR spectroscopy, whereas the presence of primary hydroxyl groups w as implied by model experiments. Multiple initiation by HES was verified by diphenyl ethylene end-capping and NMR analysis; the resulting star polymer had an average of 5.2 arms per molecule. A detailed investigation of the r eaction mechanism and the characterization of the polymers are in progress. (C) 2000 John Wiley & Sons, Inc.