The kinetics of graft copolymerization

Gamma‐ radiation induced graft copolymerization of methyl methacrylate with natural rubber is characterized by high yields of grafted polymer even at relatively high monomer concentrations. The rates are first order except at low monomer concentrations; above 95% rubber concentration the polymerization rates are very low. A reaction mechanism has heen proposed in which it is shown that these results are consistent with a relatively slow initiation step between rubber radicals and methyl methacrylate and a rapid crossed termination reaction between methacrylate radicals and rubber radicals. In order to explain the high yield of grafted polymer, it has been assumed that radicals produced from methyl methacrylate by gamma‐radiation are, unlike the growing methacrylate chains, capable of attacking the rubber molecule and thus from sites for grafting to occur, and also that monomer transfer is negligeable.