Thermal oxidative and photo-oxidative degradation of polytetrahydrofuran studied using ~1H NMR, ~(13)C NMR and GPC

摘要

The products and mechanism of the thermal oxidative degradation at 180 °C and the photo-oxidative degradation at 40 °C of polytetrahydrofuran have been investigated using 1H NMR, ~(13)C NMR and GPC. The NMR analysis was assisted by the use of DEPT ~(13)C spectra, two-dimensional NMR spectroscopy (COSY, HMQC and HMBC) and chemical shift simulation software. The NMR spectra of both thermally and photolytically degraded samples were similar showing that the degradation mechanisms were similar. GPC indicated that both chain scission, leading to lower molar mass products, and chain extension, leading to higher molar mass products, occurred initially. NMR analysis of the initial soluble degraded polymers showed that chain scission resulted in formate, aldehyde, propyl ether, butyl ether and propanoyl chain ends, and in-chain ester groups were also formed. For longer periods of degradation, crosslinked gels were formed but these were not amenable to detailed structural characterisation by high-resolution NMR to determine the crosslink mechanism.