Ferroelectric-like dielectric behavior in the piezoelectric amorphous copolymer of vinylidenecyanide and vinyl acetate.

The alternating copolymer of vinylidenecyanide and vinyl acetate is the first amorphous polymer to show a combination of excellent properties among the several known piezoelectric polymers, e.g., high piezoelectric activity (d sub (31) = 7 pC/N), high electromechanical constant (k sub (33) = 0.25) and high thermal stability (glass transition temperature, Tg = 170C). Our dielectric studies have uncovered for the first time several unusual characteristics which strongly suggest the copolymer to be a ferroelectric glass, perhaps the first of its kind in terms of technical importance. The ferroelectric nature is manifested in the dielectric anomalies (a fourteen-fold increase in the dielectric constant), the Curie-Weiss behavior and the positive-and-negative divergence of the third-order dielectric susceptibility around the transition temperature.