Ferroelectric Relaxation in a 65/35 mol% Copolymer of Vinylidene Fluoride and Trifluoroethylene

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Abstract
Dielectric relaxations associated with the ferroelectric transition have been investigated in a copolymer containing 65 mol% vinylidene fluoride and 35 mol% trifluoroethylene. The transition shows thermal hysteresis, taking place at 100°C upon heating and at 70°C upon cooling. Near the transition point, there is a peak in the dielectric relaxation strength Δ ε and a shoulder in the relaxation time τ. These anomalies and hysteresis are removed by taking the ratio of τ to Δ ε, which corresponds to the kinetic coefficient. From its Arrhenius-type temperature dependence, the activation energy is estimated to be 16 kcal/mol both below and above the transition point. The molecular motions responsible for the ferroelectric relaxation in this copolymer are thought to occur intramolecularly by a trans-gauche transformation in the crystalline regions.