Thermal and photo‐induced phenomena in γ‐irradiated poly(methyl methacrylate)

Abstract

Abstract ESR spectra and optical absorption spectra of γ‐irradiated poly(methyl methacrylate) (PMMA) at 77°K and the photo‐ and thermal bleaching behavior have been studied. γ‐Irradiation of PMMA yields a singles spectrum with a line width of 6 G which is bleachable with visible light. This species is assigned to the polymer cation. The unbleached species consists mainly of a four‐line spectrum and is assigned to a polymer radical having a different CH 2 conformation from the usual nine‐line spectrum. On subsequent warming to room temperature, the spectrum changes into the nine‐line spectrum. γ‐Irradiation of PMMA containing biphenyl as an additive at 77°K gives biphenyl cation. Yield of polymer radical is reduced by the addition of biphenyl and 2‐methyltetrahydrofuran. A mechanism is proposed which is consistent with the experimental results.