IONIC SPECIES IN IRRADIATED POLY(METHYL METHACRYLATE) - A PULSE-RADIOLYSIS AND ELECTRON-SPIN-RESONANCE STUDY

In the reported experiments, poly(methyl methacrylate) free of initiators was synthesized by gamma -irradiation and cast into transparent films. The samples were investigated by ns pulse radiolysis at various temperatures, and by ESR spectroscopy after gamma -irradiation at 77 degree K. Short-lived transients with optical absorptions at 440 and 725 nm were observed. The 440 nm absorption has been ascribed to the cation and the 725 nm absorption ( epsilon G equals 3000 m** minus **1 cm** minus **1 (100 eV)** minus **1, tau //1/////2 equals 190 ns at minus 13 degree C, E//a equals 6. 5 kcal/mol) to the anion. These assignments are based on ESR data of samples of poly(methyl methacrylate) and pivalic acid methyl ester deuterated at the ester and alpha -methyl groups, respectively, and subjected to thermal annealing and photobleaching. The anion decomposes on photobleaching by loss of the ester minus CH//3 radical, and the cation is proposed to decay by loss of the minus CH//3 radical from the alpha -methyl group. The thermal decay of the anion is discussed.