Dielectric relaxation of acrylonitrile–butadiene copolymers

Dielectric constants and losses of four kinds of acrylonitrile–butadiene copolymers of different degrees of polymerization were measured in the glass–rubber transition region. Curves of the dielectric losses against frequency showed asymmetric loss curves as often seen in α‐relaxations of polar polymers. The loci of Cole‐Cole plots of the complex dielectric constants of these copolymers fitted well the loci of Havriliak‐Negami's equation, The distribution parameters (1 − α) and β of the relaxation times were calculated. It is suggested that the mechanism of relaxation of the long chains is governed by a cooperative mechanism consisting of two concurrent motions: the first motion is the segmental relaxation of the polar chains, and the second is the induced motion of the neighboring segments successive to the first one.