Preparation and characterization of porous poly(vinylidene fluoride-trifluoroethylene) copolymer membranes via electrospinning and further hot pressing

Ferroelectric polymers, including polyvinylidene fluoride homopolymer and poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)] copolymer, have been investigated extensively due to their potential application in sensors, actuators, transducers and energy harvesting. Recently, porous ferroelectric polymers have stimulated much interest because such materials have advantages of light weight, low acoustic and mechanical impedance, and high voltage sensitivity. In this work, P(VDF-TrFE) porous membranes were prepared for the first time by electrospinning and subsequent hot pressing. The morphology of the resultant electrospun membranes (nanofibers with or without beads) can be varied depending on the concentration of polymer solution used during the electrospinning process. Differential scanning calorimetry, wide-angle X-ray diffraction and Fourier-transform infrared confirmed the automatic formation of β crystallites in the P(VDF-TrFE) electrospun porous membrane. Based on piezoelectric strain coefficient measurement, dielectric constant measurement and dynamic mechanical analysis, it was found that the hot pressed P(VDF-TrFE) electrospun membrane with beads not only had a relatively high d33 value compared with those of other electrospun P(VDF-TrFE) membranes, but also the advantage of low dielectric constant and high flexibility.