Degradation of poly(2,6-dimethylphenylene oxide) and poly(phenylene sulfide) by gamma radiation

Electron spin resonance (ESR) spectroscopy and volatile product analysis have been used to examine the degradation of poly[oxy(2,6-dimethyl-1,4-phenylene)], PPO, and poly(thio-1,4-phenylene), PPS, by γ-radiation. Radiation chemical yields (G-values) for trapped radicals were 0.60 and 0.16 after irradiation at 77K, and 0.33 and 0.04 after irradiation at 300 K, for PPO and PPS, respectively. THe ESR spectra of PPO can be analyzed in terms of PhO·, PhCH₂· and cyclohexadienyl radicals, whereas PPS contained predominantly photobleachable radical ions. G(H₂) = 0.08 and G(CH₄) = 0.015 for PPO irradiated at 300 K; G(H₂) = 0.03 for PPS. The radicals in PPO indicate main-chain scission of the Ph-O bond and loss of H from CH₃ in equal amounts. The radical ions in PPS decayed without the formation of neutral radicals indicating little bond scission and extremely high radiation resistance, which is confirmed by the low G(R) and G(H₂) values.