Mechanism of radiation‐induced degradation of poly(methyl methacrylate) as studied by ESR and electron spin echo methods

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.