Structure of poly(vinyl alcohol)-iodine complex in water swollen film

Abstract

The structure of a poly(vinyl alcohol) (PVA)-iodine complex was investigated by a resonance Raman spectroscopy, wide angle X-ray diffraction, small angle X-ray scattering, NMR and IR spectroscopies. The Raman spectra of swollen PVA films exhibited fundamental scattering at 164, 108, and 42 cm−1 with Ar+ ion and dye lasers as the excitation sources. The results of Raman spectra showed that only the I5− is formed in the complex, irrespective of the difference in the visible absorption spectra. The relative intensity of the peak at 65 ppm decreased with increasing amount of complex in the 13C NMR spectra. The absorbance of the infrared spectrum in the region of 2900–3300 cm−1 decreased with increased iodine concentration of the soaking solution, while the absorbance in the region of 3300–3700 cm−1 increased. These results show that some changes in the state of hydrogen bondings are induced by complexation. The weight of the PVA film increased rapidly by iodine sorption at the first stage and then decreased. The changes of the long period and volume took place rapidly, being followed by much slower increase in Young’s modulus. The ratio of the decrease in volume was much larger than that of the long period. It was assumed that the fast contraction in iodine-soaking was mainly due to the release of water out of membranes induced by iodine-sorption but not due to the complexation. © 1987, The Society of Polymer Science, Japan. All rights reserved.