Chain Motions in the Paraelectric Phase in Single Crystalline Films of Vinylidene Fluoride and Trifluoroethylene Copolymer P(VDF/TrFE)

An anomalously large dielectric constant and a long relaxation time along the chain axis were first observed in the paraelectric phase of a ferroelectric copolymer of vinylidene fluoride and trifluoroethylene. Dielectric, X-ray scattering and shear sound velocity studies consistently show that the anomalous phenomena arise from the characteristic motion of a chain molecule of T G T G ′ chain conformation in the crystal: the chain in the paraelectric phase rotates independently of neighboring chains, and, in the chain, a T G T G ′ sequence, whose length increases around the Curie temperature, undergoes the flip-flop motion. The crystal in the paraelectric phase is a liquid crystal of 1D liquid and 2D solid.