HEAD-TO-HEAD POLYMERS .24. SYNTHESIS OF HEAD-TO-HEAD POLYISOBUTYLENE BY GRIGNARD COUPLING REACTION

Head-to-head polyisobutylene of molecular weight 3000 to 10,000 was prepared in about 30% yield by Grignard coupling polymerization of 2,2,3,3-tetramethyl-1,4-dibromobutane with copper(I) tris(triphenylphosphino)bromide as the catalyst. The polymers were characterized and compared to the corresponding head-to-tail polymers of similar molecular weight. A substantial portion of the reaction product of the Grignard coupling polymerization was not polymeric but was identified as the cyclized product, 1,1,2,2-tetramethylcyclobutane.