Electron spin resonance studies of polycarbonate irradiated by γ‐rays and ultraviolet light

Paramagnetic species produced in polycarbonate (PC) by γ‐ or ultraviolet irradiation were investigated by ESR. In γ‐irradiation, scissions of carbonate groups in the main chain occur. ESR spectra (g = 2.0034) composed of a sharp singlet, some broad singlets, and a small signal with hyperfine structure are obtained, and they are assigned to trapped electrons, positive radical ions, phenoxy‐type free radicals, phenyl radicals, and OC6H4C(CH3)2 radicals. The G value for total yields of paramagnetic species at 77°K is 1.8. The percentage of CO and CO2, the dominant gases evolved, is 65.4 and 33.8%, respectively. In ultraviolet irradiation, energy is absorbed selectively at the surface region. The surface region becomes insoluble in methylene chloride because of crosslinking of phenyl groups. The ESR spectrum obtained at 77°K is a broad singlet and assigned to phenoxy‐type free radicals, phenyl radicals, and polyenyl‐type free radicals. Some differences in effects of γ‐ and ultraviolet irradiation of PC are discussed.