Abstract: | The role of radical species in the degradation of poly(methyl methacrylate) (PMMA) induced by γ-irradiation has been studied by means of electron spin resonance and electron spin echo spectroscopy. The major radical species generated initially at 77 K are assigned to main chain ? CH ? and side chain ? COOCH2 radicals, and ? COOCH anion radical. Only the ? COOCH2 radical converts to the scission-type ? CH2 ? C(CH3)COOCH3 radical on warming the sample of >180 K. A part of the ? CH ? radical disappears on warming the sample of >265 K. It is concluded that the scission of PMMA main chain occurs by the intramolecular process from the ? COOCH2 radical as the precursor state. |