Processing and characterization of free standing highly oriented ferroelectric polymer films with remarkably low coercive field and high remnant polarization

Highly aligned poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) films were processed using a scalable one-step melt extrusion processing route. Crystalline structure and orientation were optimized by controlling the melt extrusion conditions. XRD patterns suggested the nearly perfect alignment of the c-axis (polymer chain direction) along the extrusion direction in the optimized as-extruded films. SEM analysis confirmed the morphology of the crystalline phase, showing edge-on lamellae stacked perpendicular to the extrusion direction. DSC data indicated high crystallinity and well-ordered ferroelectric structure of the extruded films. The FTIR spectroscopy proved strong intermolecular dipole dipole interaction in the extruded films. Accordingly, the optimized as-extruded PVDF-TrFE films exhibit a coercive field of 24 kV/mm, half of the commonly reported values for bulk films (similar to 50 kV/mm) and a remnant polarization of 0.078 C/m(2) which further increased to 0.099 C/m(2) after annealing. This value is close to the theoretical limit (0.102 C/m(2)) assuming perfect in-plane c-axis orientation and 100% crystallinity. (C) 2016 Elsevier Ltd. All rights reserved.