Although the mechanism of polarization switching in crystalline ferroelectrics is well understood, there are serious difficulties in understanding the same phenomena in polymer ferroelectric films. On the other hand, a striking similarity has been observed between the latter and liquid-crystal ferroelectrics. To explain the results of our experiments on 20–200-nm-thick films of copolymer P(VDF70%-TrFE30%), a simple viscoelastic model is proposed, which seems to be quite general and can be applied to variety of organic ferroelectric materials. Our approach is based on extension to polymer and other “soft matter” ferroelectrics of the Ericksen-Leslie continuum dynamic theory well recognized in physics of liquid crystals. In soft systems the polarization switching through the viscoelastic deformation becomes more favorable than that described by the Landau-Ginzburg theory. The model operates with rotation of the polarization vector in the electric field and shows the time and field dependences of the polarization current in surprisingly good agreement with experiment. The latter allows one to extract the rotational viscosity coefficient responsible for the energy dissipation.

• Received 4 August 2010

DOI:https://doi.org/10.1103/PhysRevB.82.134122