THE EFFECTS OF PRESSURE ON THE BETA MOLECULAR RELAXATION AND PHASE-TRANSITIONS OF THE FERROELECTRIC COPOLYMER P(VDF0.7TRFE0.3)

The effects of hydrostatic pressure on the dynamics and energetics of the beta molecular relaxation process and on the ferroelectric (T(c)) and melting (T(m)) transition temperatures of the ferroelectric copolymer P(VDF0.7TrFE0.3) have been investigated. Pressure causes a large slowing down of the beta relaxation as well as large increases in T(c) and T(m), but the magnitudes of the effects are different for the different transitions. These effects can be qualitatively understood in terms of pressure-induced hinderance of the moleCUlar motions and/or reorientations that occur at the various transitions. The slowing down of the beta relaxation is interpreted in terms of the Vogel-Fulcher equation and results from increases in both the energy barrier to dipolar motion and the reference temperature (T0) for the kinetic relaxation which represents the ''static'' dipolar freezing temperature for the process. In terms of both its dynamics and energetics, the beta relaxation of the copolymer is nearly indistinguishable from that in PVDF.