Effect of crystallization temperature on the phase transitions of P(VDF/TrFE) copolymers

✍ Scribed by Rinaldo Gregorio Jr.; Marcelo Marino Botta

• Publisher: John Wiley and Sons
• Year: 1998
• Tongue: English
• Weight: 309 KB
• Volume: 36
• Category: Article
• ISSN: 0887-6266
• DOI: 10.1002/(sici)1099-0488(199802)36:3<403::aid-polb2>3.0.co;2-s

✦ Synopsis

A systematic study was carried out on the effect of the crystallization temperature (T cr ), on the phase transitions presented by P(VDF/TrFE) copolymers cast from dimethylformamide (DMF) solution with molar ratios 60/40, 70/30, and 80/20. The results obtained by differential scanning calorimetry (DSC) showed that twophase transitions are observed only when the copolymer crystallizes above a certain temperature T o , and that the temperatures at which these transitions occur are reduced slightly with T cr increase. It also was observed that when T cr increases, the intensity of the endotherm corresponding to the lowest temperature transition is increased, whereas the one corresponding to the highest temperature transition is reduced. In order to explain these phenomena, the existence of two ferroelectric and two paraelectric phases is suggested. The conformational differences between like phases occur due to the distinct origin of each one: the best organized phase crystallizes directly from solution, whereas the least organized is the result of a solid phase transition. Wide angle x-ray diffusion (WAXD) diffractograms corroborate this hypothesis. Phase diagrams for samples crystallized below and above T o have been proposed.