TEMPERATURE-DEPENDENCE OF FREE-VOLUME HOLES IN POLY(VINYL ALCOHOL) STUDIED BY POSITRON-ANNIHILATION TECHNIQUE

The temperature dependence of free-volume holes in pure poly(vinyl alc ohol) (PVA) and 30% ZnCl2-treated PVA has been studied at different te mperatures ranging from 25 to 150 degrees C. The dependence of the ele ctrical conductivity on the free-volume holes is probed by the positro n annihilation lifetime (PAL) technique. The lifetime tau(3) of the or tho-positronium (o-Ps) and its intensity I-3 were measured for the two samples below and above the glass transition temperatures (T-g). The observed shift in the T-g to lower value might be attributed to the in crease in the electrical conductivity sigma. For treated PVA, the exis tence of large ionic charge carriers can be concluded from a large val ue of the critical hole size. Copyright (C) 1996 Elsevier Science Ltd.