$gamma$-RAY INDUCED POLYMERIZATION OF METHYL METHACRYALTE IN THE PRESENCE OF POLYVINYL ACETATE

The polyvinyl acetate added was considered as a solvent of the solution, and to compare this with polyvinyl acetate, an equivalent amount of ethyl acetate, which had the same structure as the monomer unit of polyvinyl acetate, was used. The rate of the free radical production of ethyl acetate is a linear function of the chemical composition of the mixture. The ratio of the rate of solution polymerization to the rate of bulk polymerizatron (R/sub p//R/sub po/) was decreased slrghtly by the small amount of polyvinyl acetate, and then it increased rapidly with an increasing amount of polyvinyl acetate. The speed of this increase was greater in the higher molecular weight polymer system than in the case of the lower polymer. This rapid increase was attributed to the gel effect. The degree of polymeri-zation of polyvinyl acetate was only slightly influenced by the decrease of the ratio, R/sub p//R/sub po/. Thls negative acceleration phenomenon at a low concentration of the polymer was not considered to be due to the energy transfer from methyl methacrylate to polyvinyl acetate, but to the coil effect of the polymer chain in the solution. (OID)