Glassy dynamics in an electron-irradiated poly(vinylidene fluoride-trifluoroethylene) copolymer system

The dynamic processes in electron-irradiated poly(vinylidene fluoride-trifluoroethylene) [P(VDF-TrFE)], copolymer with a VDF content of 55 mol % have been studied by measurements of the temperature and frequency-dependent linear (epsilon(1)) and third-order nonlinear (epsilon(3)) dielectric constants. Analysis of the complex linear dielectric response by a temperature-frequency plot has revealed that the longest relaxation time diverges at T = 277 K, while the bulk of the relaxation times remains finite below this freezing temperature. Such an asymmetric behavior is, together with the temperature dependence of the static field-cooled dielectric constant, very similar to that observed in classical relaxor systems, such as lead magnesium niobate and lanthanum lead zirconate titanate, and is reminiscent of the dynamic behavior observed in various spin glasses. In addition, a paraelectric-to-glass crossover in the temperature dependence of the dielectric nonlinearity a(3) = epsilon(3)/epsilon(0)(3)epsilon(1)(4), typical for relaxors, has been observed.