E.s.r. studies on free radicals generated in poly[p-(2-hydroxyethoxy) benzoic acid] fibres at low temperatures

Free radicals generated in stretched and ground poly p-(2-hydroxyethoxy) benzoic acid] (PEOB) were studied by e.s.r. spectroscopy in an effort to isolate those formed by main chain scission. PEOB fibres stretched at ?86°C in a dry nitrogen atmosphere gave an asymmetric spectrum, which had patterns characteristic of both phenoxy and peroxy radicals in addition to some unknown peaks. The shape of the spectrum changed with increasing temperatures, finally becoming identical to that of phenoxy radicals at room temperature. The phenoxy radical was observed in all PEOB films ground or γ-irradiated in liquid nitrogen. In some cases a small peak of peroxy radical was observed. Theoretical spectra calculated for possible radical species or combinations of them were compared with those observed. No direct evidence was observed of the formation of alkyl type and radicals which were assumed to be formed with phenoxy radicals upon main chain rupture of PEOB. However, the relatively unstable peroxy radical observed in these experiments is thought to arise from them.