XPS and IR study of X-ray induced degradation of PVA polymer film

The X-ray induced compositional modification of a solvent cast polyvinyl alcohol [PVA, -(CH2-HCOH)n-] polymer film was studied using X-ray photoelectron (XPS) and transmission infra-red (IR) spectroscopies. While the -CH2 group was stable, the alcoholic -COH moiety was unstable under the X-ray beam (Mg K α radiation: 1253.6 eV) and reached continuosly to produce three new C(1s) peaks assignable to carbonyl C=O (oxidation), carboxylate -COO (oxidative chain scission) and ether C-O-C linkages (crosslinking, dehydroxylation). Transmission FT-IR spectra of X-ray treated films showed the carbonyl stretch at 1700 cm-1 and a loss of intensity in the O-H stretching mode near 3340 cm-1. The results indicate that degradation occurs throughout the polymer bulk and is caused either directly, by X-ray photons, or by the secondary electrons generated within the polymer. The ease with which degration can be detected is sensitive to analyzer resolution, X-ray flux and precautionary measures.