Anomaly in dielectric relaxation in alternating copolymers of vinylidene cyanide and fatty acid vinyl ester

Abstract 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.