Structure of solution grafted polybutadiene

Three different polybutadienes possessing widely different vinyl and cis monomer structures have been grafted with methyl methacrylate in solution using both benzoyl peroxide and azobisisobutyronitrile catalysts. Careful fractionation and backbone degradation techniques together with molecular weight determinations lead to the conclusions that both catalysts gave graft copolymer in the 10% rubber solutions used. Benzoyl peroxide always gave better graft efficiencies, (as did high vinyl and to a lesser extent high cis polybutadiene). The molecular weight of the polymethylmethacrylate grafts are slightly lower than those of homopolymers polymerized under the same conditions indicating < 20% grafting by chain transfer and termination mainly by disproportionation.