Abstract
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. Head‐to‐head polyisobutylene is crystalline, with a Tm of 187°C and a Tg of 87°C and still has bromine end groups left. The polymers have been characterized by their infrared, 1H‐, and 13C‐NMR spectra 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 is not polymeric but was identified as cyclized product, 1,1,2,2‐tetramethylcyclobutane.