Block and graft copolymers by selective cationic initiation. II. Synthesis and characterization of styrene‐isobutylene block copolymers by use of chlorobrominated alkanes

Abstract

Abstract The synthesis and characterization of a new block copolymer, poly(styrene‐ b ‐isobutylene) (PSt‐ b ‐PIB), is described. The synthesis involves the initiation of an isobutylene polymerization by a polystyrene molecule containing a terminal tertiary bromine (PSt‐Br), in conjunction with diethylaluminum chloride coinitiator. The species PSt‐Br is in turn synthesized by initiating the polymerization of styrene selectively by the tertiary chlorine of the 2‐bromo‐6‐chloro‐2,6‐dimethylheptane/Et 3 Al initiator system in the absence of chain transfer. The conditions conducive for selective initiation by tertiary chlorine have been worked out. The pure block copolymer, PSt‐ b ‐PIB, is obtained by selective extraction and some of its properties were determined, e.g., solubility and film behavior, T g , and intrinsic viscosity versus temperature. The intrinsic viscosity (in toluene) exhibits a maximum and a minimum in the temperature range from 15 to 55°C.