The influence of PPVE/PMVE/CFE monomers insertion on the ferroelectric behavior of the P(VDF-TrFE)-based electroactive terpolymers

Abstract

The perfluoroalkyl ethylene ether (PMVE), perfluoro propoxyethylene (PPVE), and chlorofluoroethylene (CFE) (<4 mol%) as the third monomers are embed into the ferroelectric polyvinylidene-trifluoroethylene (P(VDF-TrFE)), respectively, aiming to modify the ferroelectric behaviors of the copolymers. Through calculation, we find the PPVE and PMVE molecular segments possess a large free volume but a low polarity, effective promoting the formation of all-trans β phase in the crystal region of P(VDF-TrFE), and contributing to the high maximum and remnant polarization (P_s and P_r) of related P(VDF-TrFE-PPVE) (∼6.8 and 6.3 μC cm⁻²) and P(VDF-TrFE-PMVE) (∼5.6 and 5.0 μC cm⁻²) under 200 MV m⁻¹, respectively. Differently, the CFE segment provides not only a large volume but also a high polarity, resulting in the phase transition from β to α and thus, the target terpolymer P(VDF-TrFE-CFE) appears a transition from ferroelectrics to relaxor ferroelectrics, and shows a high dielectric permittivity (ε_r∼55.4) at 100Hz. This work may provide a comprehensive insight of modifying the structures of P(VDF-TrFE), offering crucial guidance for optimizing the design of this type ferroelectric materials.