Control of crystal morphology and its effect on electromechanical performances of electrostrictive P(VDF-TrFE-CTFE) terpolymer

Abstract

Interplay of microstructure and electromechanical properties of the poly(vinylidenefluoride-trifluoroethylene-chlorotrifluoroethylene) (P(VDF-TrFE-CTFE)) terpolymer were studied by tailor-made adjusting crystal fraction via temperature annealing processing. Worm-like crystal nanodomain firstly demonstrated an evolution of the surface morphology upon the increasing temperature annealing treatment, in favor of preferential crystal orientation, known to facilitate the dipoles switching along the external electric field. Apart from the aligned crystal orientation and high coverage of crystal fraction raised by high temperature annealing, the enhancement of interphase fraction of the terpolymer contributes to the high-performance of dielectric property and increases the electric breakdown strength as well. The electromechanical behaviors linking to the microstructure were finally evaluated by a bilaminar unimorph cantilever beam theory. And consequently the figure of merits of electromechanical performance, namely dielectric constant and tensile strength values play a trade-off role in the field-induced strain of the electroactive terpolymer layer, suggesting the microstructure-controlled effects. The tip displacement of bilaminar cantilever beam, serving as an indicator of the actuator performance, consists in the electroactive terpolymer layers and passive foil support. Aiming at obtaining optimum actuator device, specific microstructure of terpolymer membrane was revealed by taking the passive support layers into consideration.