Dielectric dispersion and phase transitions in vinylidene fluoride-trifluoroethylene copolymer ferroelectric films

Dielectric properties and phase transitions in bulk films of ferroelectric vinylidene fluoride-trifluoroethylene copolymers of different composition ( 75 : 25, 60 : 40, 55 : 45) were studied. The samples were prepared by spin- coating, from solution. In films of 55 : 45 composition, a second-order pha se transition was observed. The samples of 75 : 25 and 60 : 40 composition exhibit the first-order phase transitions. Ultrathin films with a compositi on of 55 : 45 and a thickness of 50 Angstrom (similar to 10 monolayers) wer e obtained by the Langmuir-Blodgett method. In contrast to bulk films, Lang muir-Blodgett films exhibit the first-order phase transition with hysteresi s and shift of the phase transition point to high temperatures. Probably, t his is associated with the high crystallinity of Langmuir-Blodgett films.