Add time:08/23/2019         Source:sciencedirect.com

Poly[(2-cyanoethyl vinyl ether)-co-(vinyl alcohol)] is a polymer with a higher dielectric constant (ε = 15 at 1 kHz) at room temperature and is therefore used as a binder in electroluminescent lamps. Two different dipole relaxations are observed: a β relaxation, associated with the rotation of the cyanomethyl moiety, at temperatures below 273 K; and an α relaxation at the glass-rubber transition temperature (291 K). The high- and low-frequency limits of the dielectric constant for the β relaxation are observed to be 3.4 and 9.5, respectively. There is good agreement between the observed molecular dipole moment (12.1 × 10−30 C m) derived from the temperature dependence of the static dielectric constant at high temperatures and the literature values for the dipoles present in the polymer. Finally, it is shown that an accurate determination of the characteristic relaxation time for the β relaxation demands fitting to a proper model because using merely the maximum of the imaginary part of the dielectric constant might lead to erroneous results.

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