The role of high pressure in the study and applications of the ferroelectric polymer polyvinylidene fluoride and its copolymers

摘要

The effects of frequency, temperature and hydrostatic pressure on the dielectric properties, molecular relaxations, and phase transitions of PVDF and a copolymer with 30 mol% trifluoroethylene will be discussed. Pressure causes large slowing down of the /spl beta/ molecular relaxations as well as large increases in the ferroelectric transition temperatures and melting points, but the magnitudes of the effects are different for the different "transitions." These effects can be understood in terms of pressure-induced hindrance of the molecular motions and/or reorientations. A unique application of these polymers as time-resolved dynamic stress gauges based on PVDF studies under very high pressure shock compression is discussed.