Dielectric relaxations in a copolymer of vinylidene fluoride and trifluoroethylene

Dynamic dielectric measurements were carried out for a copolymer of vinylidene fluoride (55 mol %) and trifluoroethylene (45 mol %) over the frequency range of 50 Hz–50 MHz at temperatures between −15 and 130 °C. Observed relaxations associated with a crystalline phase transition at 70 °C were found to fit the Cole-Cole arc with a distribution of relaxation times. The equilibrium dielectric constant e(0) shows a dielectric anomaly in that it rapidly increases to 70 just below 70 °C and then decreases. The logarithm of the observed relaxation time t vs 1/T (K−1) shows a shoulder near 70 °C which is interpreted as being the result of a critical slowing down phenomenon. The derived relaxation time t0 in the absence of cooperative effects exhibits an Arrhenius type temperature dependence from 40 to 130 °C with a potential barrier for dipole rotation of 13 kcal/mol.