Cationic polymerization with boron halides. V. Synthesis of poly(isobutylene‐b‐styrene) and poly(styrene‐b‐isobutylene)

Abstract

Abstract Block copolymers of isobutylene and styrene, PIB‐ b ‐PSt and PSt‐ b ‐PIB, have been prepared by a two‐step synthesis involving (1) preparation of terminally chlorinated (telechelic) polyisobutylene or polystyrene “prepolymers” by using the H 2 O/BCl 3 initiator system and (2) blocking from these telechelic prepolymers a second polymer segment by using an alkyaluminum, e.g., Et 2 AlCl coinitiator. The telechelic polyisobutylene and polystyrene contain tertiary and benzylic chlorine termini, respectively. Block copolymer characterization included detailed selective solvent extraction procedures, coupled with GPC determinations, PMR, solubility, and intrinsic viscosity studies. The synthesis of PIB‐ b ‐PSt and PSt‐ b ‐PIB provides direct chemical evidence for the presence and position of active chlorine termini in BCl 3 ‐coinitiated olefin polymerizations.