ANOMALY IN DIELECTRIC-RELAXATION IN ALTERNATING COPOLYMERS OF VINYLIDENE CYANIDE AND FATTY-ACID VINYL ESTER

Dielectric relaxation spectra at 10 Hz to 1 MHz for five vinylidene cyanide-vinyl ester copolymers were studied as functions of temperature and length of aliphatic side-chain in the comonomer unit. Three unusual phenomena in their dielectric behaviours were found: (1) extremely large dielectric relaxation strength; (2) dielectric transition phenomena whose strength changed suddenly at a critical temperature; and (3) unusual temperature dependence of the strength above the transition temperature. The dielectric transition temperature depends upon length of the side-chain and corresponds well with enthalpy peak temperature in the differential scanning calorimetry study. It was also found that the thermal history strongly affects the dielectric behaviours. © 1990.