Low frequency ac conduction and dielectric relaxation behavior of solution grown and uniaxially stretched poly(vinylidene fluoride) films

The measurements of ac conductivity [sigma(m)(omega)] dielectric constant [epsilon'(omega)] and loss [epsilon(omega)] have been performed on solution grown (thickness similar to 85 mu m) and uniaxially stretched (thickness similar to 25, 45 and 80 mu m) films of poly(vinylidene fluoride) (PVDF) in the frequency range 0.1 kHz-10 MHz and in the temperature range 77-400 K. The sigma(m)(omega) can be described by the relation sigma(omega) = A omega(s), where s is close to unity and decreases with increase in temperature. Three relaxations, observed in the present investigation, have been designated as the alpha(c)-, the alpha(a)- and the beta-relaxations appearing from high temperature side to the low temperature side. The alpha(c)-relaxation could not be observed in the case of uniaxially stretched poly(vinylidene fluoride) films. The alpha(c)- and alpha(a)-relaxations are associated with the molecular motions in the crystalline regions and micro-Brownian motion in the amorphous regions of the main polymer chain, respectively, whereas the beta-relaxation is attributed to the rotation of side group dipoles or to the local oscillations of the frozen main polymer chain. (c) 2006 Elsevier Ltd. All rights reserved.