Direct spectroscopic evidence of field-induced solid-state chain conformation transformation in a ferroelectric relaxor polymer

Ferroelectric relaxor P(VDF-TrFE-CFE) terpolymer can generate a hysteresis-free polarization of 47mC∕m2 at an electric field of 100MV∕m and is attractive for many potential actuating and sensing applications. Fourier transform infrared spectra under electric field reveal that this large polarization originates from the field-induced crystalline phase transformation. The nonpolar TGTG′ chain conformation in P(VDF-TrFE-CFE) can be converted into polar trans (Tm>4 and T3G) conformation under high electric field and the latter can be effectively aligned to the applied field direction. Furthermore, this conformation transformation is completely reversible and no hysteresis can be observed during the switching of applied electric field. In contrast, normal ferroelectric polymer P(VDF-TrFE) exhibits square polarization loop with very small reversible polarization.