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 T-c0 = 80 +/- 10 degrees C, double hysteresis loops between T-c0, and the critical temperature T-cr = 145 +/- 5 degrees C, and no hysteresis above T-cr where the critical electric field is E-cr = 0.93+/-0.1x10(9) V/m.