CURIE TRANSITION, FERROELECTRIC CRYSTAL-STRUCTURE, AND FERROELECTRICITY OF A VDF/TRFE(75/25) COPOLYMER .1. THE EFFECT OF THE CONSECUTIVE ANNEALING IN THE FERROELECTRIC STATE ON CURIE TRANSITION AND FERROELECTRIC CRYSTAL-STRUCTURE

We have completely deconvoluted multiple ferroelectric-to-paraelectric phase transitions of a VDF/TrFE copolymer often observed on DSC by consecutive annealing below the Curie transition temperature and obtained three clear endothermic peaks resolved well from each other. We could also increase the Curie transition temperature by using the consecutive annealing performed in the ferroelectric state. Annealing time, as well as annealing temperature, was found to affect the Curie transition behavior significantly. Each ferroelectric crystalline phase was characterized by IR, Raman scattering, x-ray diffraction, and DSC measurements. The ferroelectric phase, having higher Curie transition temperature, has been found to have more trans sequences and less gauche defects and to require larger thermal energy for the Curie transition. (C) 1994 John Wiley and Sons, Inc.