Beta Phase Instability In Poly(Vinylidene Fluoride/Trifluoroethylene) Thin Films Near Beta Relaxation Temperature

The beta phase stability in poly(vinylidene fluoride/trifluoroethylene) [P(VDF-TrFE)] thin films was studied below 300K using X-ray diffraction and polarization-electric-field (P-E) hysteresis loops measurements. On as-grown samples, an irreversible partial order-disorder transformation at T-beta similar to 250K, namely, the beta relaxation temperature, was evidenced by the appearance of an additional X-Ray diffraction peak above T-beta as well as changes on the P-E loops on heating after the first cooling. This order-disorder-like transformation which is attributed to an all-trans order to helical disorder transition is suggested to take place in defect-rich regions like crystal-amorphous interphases and/or crystalline areas with randomly distributed TrFE defect-like units. (C) 2015 AIP Publishing LLC.