RAMAN SPECTRAL STUDY OF SOLID AND DISSOLVED POLY(VINYL ALCOHOL) AND ETHYLENE-VINYL ALCOHOL COPOLYMER

We have measured the Raman spectra of ethylene-vinyl alcohol copolymer (EVOH) and poly (vinyl alcohol) (PVOH). Spectra of 88% hydrolyzed PVOH were examined from the partially crystalline solid, from PVOH dissolved in both H2O and D2O, and from films precipitated from these solutions. The spectrum in H2O differs from that of the starting material by disappearance of sharp bands having Raman shift values of 1146 and 1093 cm-1, strengthening of a band near 915 cm-1, decrease in frequency of bands at 480, 1356, and 1441 cm-1, and increase in frequency of bands at 369, 413, 1023, 1371, and 2910 cm-1. The spectrum of the film shows partial reversal of these trends. With D2O as the solvent, the band shifts are slightly different from those listed above and new bands appear. These changes are indicative of loss of crystallinity, change in stereochemistry, and partial deuteration of hydroxyl during dissolution of this PVOH sample at room temperature. (C) 1994 John Wiley & Sons, Inc.