CHANGE OF POLY(VINYL ALCOHOL) CRYSTAL-LATTICE BY IODINE SORPTION

Poly(vinyl alcohol) films (PVA) were soaked at 20°C in aqueous I-KI solutions with different iodine concentrations. Iodine sorption obeyed a Freundlich isotherm over a range of iodine concentration from 5×10−3 to 6×10−1 mol l−1. Changes in the PVA crystal lattice with iodine sorption showed that iodine molecules intrude into crystalline, as well as amorphous regrons to form a new “substitution type” crystal lattice. In this lattice, one PVAchain of a hydrogen-bonded pair in the original PVA cell isreplaced by a polyiodine chain. The iodination increased the drawability of PVA films. It is not certain, however, whether the enhanced drawability is due to the plasticized amorphous phase alone, as is suggested by depression of the glass transition temperature, or also to the iodinated crystals. © 1990, The Society of Polymer Science, Japan. All rights reserved.