Structural and property changes of high energy proton-irradiated poly(vinylidene fluoride-trifluoroethylene) 56/44 mol.% copolymer

High-energy proton irradiation with a broad range of dosages has been carried out to investigate the potential for modifying the properties of poly(vinylidene fluoride-trifluoroethylene) 56/44 mol.% copolymer films. The relative permittivity, polarization hysteresis, electric field induced strain, lattice spacing and phase transition behavior of the irradiated copolymer films were studied. With regards to the dielectric and polarization behaviors, the copolymer film can be converted from a typical ferroelectric to a relaxor ferroelectric upon irradiation. This implies that the high-energy protons can break up the coherent polarization domains in the normal ferroelectric copolymer into nano-sized regions. Besides, the XRD data showed that the solid-state phase transition from the polar phase to nonpolar phase is induced in the copolymer during irradiation in which the lattice spacing increases significantly. The electric field induced phase transformation of the nano-sized regions between the polar and nonpolar phase leads to a high electrostrictive strain observed in the irradiated copolymers.