Critical point in ferroelectric Langmuir-Blodgett polymer films

The ferroelectric critical point has been found in a ferroelectric polymer by exploring the influence of the electric field on the paraelectric-ferroelectric phase transition. Dielectric and pyroelectric measurements on 30-monolayer-thick films of the crystalline copolymer poly(vinylidene fluoride-trifluoroethylene) grown by Langmuir-Blodgett deposition show a single hysteresis loop below the zero-field phase transition temperature Tc0=80±10 °C, double hysteresis loops between Tc0 , and the critical temperature Tcr=145±5 °C, and no hysteresis above Tcr where the critical electric field is Ecr=0.93±0.1X109 V/m