Formation of graft polymers by γ‐irradiation of natural rubber latex and methyl methacrylate

Exposure of mixtures of natural rubber latex and methyl methacrylate to γ‐radiation from a Co‐60 source results in polymerization of the methyl methacrylate to give a mixture of the homopolymer and grafted polymer. The ratio of grafted polymer to homopolymer and the molecular weight of the homopolymer are both considerably higher than in similar systems where polymerization was initiated by a redox catalyst. The ability of the irradiated to form continuous films on drying is much greater than that of corresponding redox‐polymerized systems. This difference is attributed primarily to the location of the polymerized methyl methacrylate throughout the individual latex particles, the polymerized methacrylate being more uniformly distributed in the case of the irradiated latex. Use of polymerization retarders which are soluble in methyl methacrylate swollen rubber supplies evidence that an increased proportion of the polymerized methacrylate is located in the surface regions of the latex particles. Conversely, a more uniform distribution of the polymer is obtained by the use of water‐soluble retarders. The probable significance of these results in relation to emulsion copolymer systems is pointed out.