Structural changes and phase behavior of electron-irradiated poly(vinylidene-trifluoroethylene) copolymers

摘要

The effect of high-energy electron irradiation on poly(vinylidene-trifluoroethylene) P(VDF-TrFE), copolymer of 56/44 comonomer molar ratio is studied using differential scanning calorimetry (DSC), X-ray diffraction (XRD) and thermally stimulated depolarization current (TSDC). DSC results show that the energy necessary to process ferroelectric transition decreases after irradiation, which indicates that high-energy electron irradiation makes ferroelectric phase less stable, causing transition to paraelectric phase at a temperature below melting point. XRD data show that the peak at 2theta = 19degrees gradually disappears with the increase of absorbed dose, which indicates that the transition from all-trans ferroelectric state to a trans-gauche amorphous conformation takes place. It is found that both the peak temperature and released charge carrier density decrease with the irradiation doses in TSDC spectra, demonstrating less dipoles and crystalline regions in the irradiated copolymer films during ferro-paraelectric (F-P) transition. The results of TSDC measurements are related to the morphological changes induced by electron beam (EB) irradiation as well as the presence of local polar ordering and decrease of crystallinity revealed in DSC and XRD results. (C) 2003 Elsevier B.V. All rights reserved. References: 32