STUDY OF FREE-RADICALS IN POLY(DIETHYLENE GLYCOL BIS(ALLYL CARBONATE)) IRRADIATED BY GAMMA-RAYS

Free radicals in poly(diethylene glycol bis(allyl carbonate)), commerc ially known as CR-39 resin, cured by radical mechanism with various am ounts of diisopropyl peroxydicarbonate were studied by electron parama gnetic resonance (e.p.r.) spectroscopy. It was found that the radicals can survive in the unirradiated polymer network for at least 6 months after polymerization. The dependence of the amplitude of the e.p.r. s ignal on the dose for CR-39 polymer irradiated by Co-60 gamma rays was found to show a maximum which increased in magnitude and shifted in p osition to higher doses for samples cured with lower initiator concent ration. This behaviour is explained by examining the role of residual allyl groups present in the cured polymer and the scission of the netw ork at the carbonate group. It was found that the refractive index inc rease observed in the irradiated polymer cannot be directly attributed to the presence of free radicals in the network.