Thermal and Photo-Induced Reactions of Polymer Radicals in γ-Irradiated Poly(alkyl methacrylate)

Abstract

Thermal and photo-induced reactions of radical species generated by γ-irradiation of poly(methyl methacrylate) and poly(ethyl methacrylate) have been investigated by means of ESR spectroscopy. The γ-irradiation at cryogenic temperature leads to the formation of three major radical species, side chain –COOCnH2n+1·− anion radicals and –COOĊHCn−1H2n−1 radicals, and main chain –ĊH– radicals. Cation radicals are immediately converted to the neutral radicals by proton transfer to the polymer molecules. Illumination of the polymer anion radicals with visible light leads to electron detachment or the elimination of ester alkyl groups to form alkyl radicals. Illumination with UV light leads to the conversion of the –COOĊHCn−1H2n−1 radicals to acyl-type –Ċ=O radicals. Both the –COOĊHCn−1H2n−1 and the –Ċ=O radicals are the precursor of scission-type ·C(CH3)(COOCnH2n+1)CH2- radicals.