Cooperative motions in PVC studied by thermally stimulated currents: Comparison with ac dielectric derivative analysis

摘要

The thermally stimulated current-thermal sampling (TSC-TS) technique was used to study the broadened glass transition in conventional "atactic" poly(vinyl chloride), PVC. The activated parameters obtained from the TSC-TS data, mainly the apparent activation energy (E-a), characterize the breadth of glass transitions in a very sensitive way. These results are compared with those values of E-a obtained from the literature, using a recently proposed method of analyzing a.c. dielectric constants and their derivatives, over the temperature range of -100-130 degrees C. Both techniques detect weak cooperative glass transition-like relaxations well below the main glass transition of ca. 80 degrees C. As is the case with "atactic" PMMA, the data suggest that compositional heterogeneity related to a small fraction of predominantly isotactic sequences contribute to the broad glass transition extending ca. 60 degrees C below the main glass transition in atactic PVC. (C) 1998 John Wiley & Sons, Inc. [References: 31]