O-17 NMR investigation of oxidative degradation in polymers under gamma-irradiation

The gamma -irradiated-oxidation of pentacontane (C50H102) and the polymer p olyisoprene was investigated as a function of oxidation level using O-17 nu clear magnetic resonance (NMR) spectroscopy. It is demonstrated that by usi ng O-17 labeled O-2 gas during the gamma -irradiation process, details abou t the oxidative degradation mechanisms can be directly obtained from the an alysis of the O-17 NMR spectra. Production of carboxylic acids is the prima ry oxygen-containing functionality during the oxidation of pentacontane, wh ile ethers and alcohols are the dominant oxidation product observed for pol yisoprene. The formation of ester species during the oxidation process is v ery minor for both materials, with water also being produced in significant amounts during the radiolytic oxidation of polyisoprene. The ability to fo cus on the oxidative component of the degradation process using O-17 NMR sp ectroscopy demonstrates the selectivity of this technique over more convent ional approaches. (C) 2001 Elsevier Science Ltd. All rights reserved.