Effect of electron irradiation on poly(vinylidene fluoride-trifluoroethylene) copolymers

Electrical field-induced strain response of electron-irradiated poly(vinyli dene fluoride-trifluoroethylene) copolymer has been studied by a Mach-Zehnd er type heterodyne interferometer in the frequency range of 3-9 kHz. The el ectrostrictive constant is calculated from the strain results, which is of the same order of magnitude as those obtained at 1 Hz by a bimorph-based st rain sensor but at much lower electrical field. Changes in the dielectric p roperty, phase transition behavior and crystal structure of the same copoly mer have also been studied. The reversible solid-state transition between t he polar and nonpolar phase in the crystalline regions of the copolymer dri ven by the external electric field is suggested to be responsible for the s ignificant high electrostrictive strain of the electron-irradiated copolyme r. (C) 2000 American Institute of Physics. [S0003-6951(00)04235-2].