STRUCTURE AND PROPERTIES OF POLY(VINYL ALCOHOL) IODINE COMPLEX FORMED IN THE CRYSTAL PHASE OF POLY(VINYL ALCOHOL) FILMS

The structure and optical properties of the complex formed in the crystal phase of PVA that is caused by soaking at very high iodine concentration are investigated. In the resonance Raman spectra of lightly and heavily iodinated specimens, two Raman shifts appeared at 109 and 161 cm-1. The 109 cm-1 peak due to the I3- mode was much stronger than the 161 cm-1 peak in a heavily iodinated specimen, whereas the peak was comparable with the 161 cm-1 peak in a lightly iodinated specimen. The complex formed in the crystal phase is identified as the I3- mode complex. It has an averaged iodine-iodine distance of 3.2 angstrom, which is different from the 3.08 angstrom of the I5- mode complex formed in the amorphous phase. The effect of KI concentration in the soaking solution on the formation of the complex is also examined. The increased KI concentration in the soaking solutions at a fixed iodine concentration increases the amount of the complex formed in the crystal phase. The change in the hydrogen-bonding state in the crystal phase with the complex formation can be evidenced by IR and NMR. (C) 1994 John Wiley & Sons, Inc.