Dielectric study of the relaxor ferroelectric poly(vinylidene fluoride-trifluoroethylene) copolymer system - art. no. 184103

The high-energy electron irradiated poly(vinylidene fluoride-trifluoroethyl ene), P(VDF-TrFE), copolymer exhibits many features resembling the relaxer ferroelectric behavior. In polymer systems, there are local dipolar motions at the monomer or unit cell scale, which manifest themselves as various re laxation processes. in this paper we investigate the relationship between t he relaxer ferroelectric behavior, especially, Vogel-Fulcher (V-F) behavior and these local dipolar relaxation processes in irradiated P(VDF-TrFE) 65/ 35-mol % copolymer. In order to cover the change in polarization dynamics o f the copolymer system, the dielectric behavior of copolymer is measured ov er a broad frequency (0.01 Hz-10 MHz) and temperature (-40 to 80 degreesC) range. The results indicate that there is an increased coupling among the l ocal dipolar motions with reduced temperature in the crystalline region. On the other hand, the randomness introduced in the irradiation prevents the formation of a polar phase, on both the macroscale and the microscale, in t he polymer. The observed relaxer behavior is a consequence of the competiti on of these two effects. The results further show that the V-F process of t he irradiated copolymer system is different from the glass transition. whic h occurs in the amorphous phase of the copolymer.