Investigation of the effect of epoxide structure on the initiation efficiency in isobutylene polymerizations initiated by epoxide/TiCl 4 systems

Abstract

The effect of the chemical structure of styrene-based epoxides, namely, styrene epoxide (SE), α-methylstyrene epoxide (MSE), p-methylstyrene epoxide (pM-SE) and α-methyl- p-methylstyrene epoxide (pM-MSE), in conjunction with TiCl 4, on the initiation efficiency ( I eff) in the carbocationic polymerization of isobutylene (IB) was investigated. SE yielded living polymerization, but the initiation efficiency was low when compared to MSE ( I eff=8% and 35%, respectively). pM-SE led to non-living IB polymerization, while pM-MSE revealed linear M n-conversion plot and narrow MWD with a non-linear first order rate plot. Among the epoxides investigated, MSE was the best initiator to scale up the one-step synthesis of polyisobutylenes (PIBs) carrying one primary hydroxyl head group and one tertiary chloride end group. The hydroxyl functionality of these PIBs determined by 1H-NMR was F n =1.09±0.16 from 24 experiments.