High-molecular-weight isobutene-isoprene copolymers containing unusually high isoprene content

摘要

The 1:2 adduct of the highly electrophilic borane B(C6F5)(3) with n-decanoic (stearic) acid, n-C17H35CO2H-B(C6F5)(3)(2) exhibits sufficiently enhanced acidity that it is an excellent initiator for the carbocationic copolymerization of isobutene with isoprene in methylene chloride and methyl chloride. High conversions to gel free, high-molecular-weight copolymers containing up to 15 wt.- isoprene are readily obtained, consistent with the anion n-C17H35CO2-{B3C6F5)(3)}(2)(-) being very weakly coordinating. Thus chain transfer following IP incorporation into the growing polymeric chain. which normally results in low average molecular weights, is much less of a factor here.