Large Dielectric Relaxations in an Alternate Copolymer of Vinylidene Cyanide and Vinyl Acetate

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Abstract
An alternate copolymer of vinylidene cyanide and vinyl acetate has been investigated dielectrically at temperatures above T g ∼170°C. A remarkable relaxation was observed in the 1 Hz to 10 kHz frequency range due to a separation from coexisting contributions as a result of the dc conductivity. The relaxation time depends upon the temperature in the WLF according to the characteristics of the micro-Brownian motions of molecular segments. The relaxation strength was found to reach 125, resulting in an unusually high dielectric constant. Such a large relaxation strength is an indication of some cooperative effects in relation to dipolar motions. Cooling to below T g in the presence of a high electric field creates a large remanent polarization which is consistent with the strong piezoelectric activity reported for this copolymer.