Influence of degree of crystallinity and syndiotacticity on infrared spectra of solid PVA

Abstract

Abstract The influence of the degree of crystallinity and the syndiotacticity on the 1145, 1095, and 916 cm −1 bands was studied. The intensity of the 1145 cm −1 band increased with increasing syndiotacticity at a low degree of crystallinity and with an increasing degree of crystallinity for a sample with syndiotacticity. The intensity of 1095 cm −1 band increased with increasing syndiotacticity at a fixed degree of crystallinity and was independent of the degree of crystallinity for a sample. The intermolecular hydrogen bonds were found to play an important role. The differences of the relations between the absorbance ratio D 1145 / D 1095 and the degree of crystallinity with syndiotacticity were explained. The extent of the decrease of the intensity of 916 cm −1 band with an increasing degree of crystallinity increased with decreasing syndiotacticity. The predominant introduction of syndiotactic sequences in the crystals was assumed in the lower syndiotacticity. The improved equation between the syndiotactic diad content in percent [ s ‐(diad) %] and the absorbance ratio D 916 / D 849 was established as s ‐(diad) % = 71.1 × ( D 916 / D 849 ) 0.327 for the films heated at 50°C with use of a syndiotactic diad content obtained from NMR spectra. © 2001 John Wiley & Sons, Inc. J Appl Polym Sci 82: 1291–1298, 2001