INITIATION VIA HALOBORATION IN LIVING CATIONIC POLYMERIZATION .2. KINETIC AND MECHANISTIC STUDIES OF ISOBUTYLENE POLYMERIZATION

We have discovered that in the presence of a proton trap to trap protic impurities, BCl3 alone can initiate the polymerization of isobutylene, leading to low molecular weight asymmetric telechelic polyisobutylenes carrying a BCl2 head group and a tertiary chloro end group. Two polymerization schemes are proposed to explain the results, one based on initiation by self-dissociation of BCl3 and another involving haloboration-initiation. Kinetic and mechanistic studies support the proposed new initiation mechanism via haloboration and explain the apparent livingness of the polymerization.