INVESTIGATION OF DIELECTRIC RELAXATIONS ASSOCIATED WITH THE GLASS-TRANSITION OF VINYLIDENE FLUORIDE AND TRIFLUOROETHYLENE COPOLYMERS BY THERMALLY STIMULATED CURRENT

Thermostimulated current (TSC) spectroscopy was applied to the charact erization of dielectric relaxations associated with the glass transiti on of a series of P(VDF/TrFE) copolymers. The maximum temperature of t he P-mode increases slightly as the TrFE unit content is increased, in the same manner as the glass transition temperature. By using the tec hnique of fractional polarizations to the resolution of this relaxatio n mode, we have isolated, for all the polymers investigated, a series of elementary relaxation times that obey a compensation law. This beha vior is characteristic of the free amorphous phase of polymers. The me an activation energy of this mode increases as the TrFE unit content i s increased, due to a stiffening of molecular chains. Annealing of the copolymers above their ferroelectric-to-paraelectric transition induc es a strong crystallinity increase of the materials. As a matter of fa ct, the amorphous phase is squeezed in to dimensions lower than the ch aracteristic length scale associated with the glass transition. (C) 19 95 John Wiley & Sons, Inc.