Second-Order dielectric constant of a copolymer of vinylidene fluoride and trifluoroethylene (52:48 mole ratio)

Abstract

The second-order dielectric constant ε2 of a copolymer of vinylidene fluoride and trifluoroethylene (52:48 in mole) was measured by means of the difference frequency method. ε2 is related to spontaneous polarization Ps and the linear dielectric constant ε1 through a thermodynamic representation of free energy. The relation explains the observed temperature dependence of ε2. ε2 was found to be proportional to the remanent polarization Pr. This is interpreted by the model thatthe ferroelectric crystal is composed of parallel and antiparallel domains. ε2 in the crystal was deduced from that of the whole polymer on the assumption of theellipsoidal crystal model. © 1987 The Society of Polymer Science, Japan. All rights reserved.