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 T₂₀=8010^, double hysteresis loops between T₂₀, and the critical temperature T₂ₑ=1455^, and no hysteresis above T₂ₑ where the critical electric field is E₂ₑ=0. 930. 110^9V/m.