ESR studies of degradation in polymers. I. γ-irradiation of poly(styrene-co-methyl methacrylate) at 77°k
| Autor: | P. J. Pomery, J. H. O'Donnell |
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| Rok vydání: | 2007 |
| Předmět: | |
| Zdroj: | Journal of Polymer Science: Polymer Symposia. 55:269-278 |
| ISSN: | 1936-0959 0360-8905 |
| Popis: | The ESR spectra, due to trapped radicals produced by γ-irradiation at 77°K, of random copolymers of styrene and methyl methacrylate of known composition and of the two parent homopolymers have been studied at 77°K. The yields of trapped radicals in the polymers were measured at several doses by double integration of the ESR spectra, and the G values for the production of radicals were calculated. The G(R) value for poly(methyl methacrylate) was calculated as 0.58 ± 0.2 and that for polystyrene as 0.05 ± 0.02. The variation of G(R) is not linear with polymer composition and is explained by a protective effect of the aromatic component resulting from energy transfer. Other chemical reactions and scavenging effects can be eliminated by consideration of the results from the analysis of the ESR spectra of the copolymers in terms of the homopolymers. It appears that different transfer mechanisms become operable as the copolymers are warmed up after irradiation at 77°K. |
| Databáze: | OpenAIRE |
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