Radiolysis of polymethyl isopropenyl ketone

Polymethyl isopropenyl ketone (PMIPK) undergoes random chain scission when irradiated at 23°C. with gamma rays or with ultraviolet light. Total energy absorption per chain scission, Ed, is 94 e.v./scission for PMIPK powders irradiated in vacuo with spent reactor fuel element gamma rays (0.42 Mrad/hr.). Ed is 84 e.v./scission for a PMIPK powder irradiated in vacuo with Co60 gamma rays (0.109 Mrad/hr.). The presence of air lowers the value of Ed to 41 e.v./scission under the former conditions. A film of PMIPK irradiated in air with 2537‐A. wavelength light exhibits Ed = 22 e.v./scission or a quantum yield ϕd = 0.22 chain scissions/absorbed photon. The viscosity‐average molecular weights of this film vary with light exposure in accordance with theoretical predictions.