Processing and Characterization of Free Standing Highly Oriented Ferroelectric Polymer Films with Remarkably Low Coercive Field and High Remnant Polarization

Abstract

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 (∼50 kV/mm) and a remnant polarization of 0.078 C/m2 which further increased to 0.099 C/m2 after annealing. This value is close to the theoretical limit (0.102 C/m2) assuming perfect in-plane c-axis orientation and 100% crystallinity.