Molecular Motion and Dielectricity in Polymers with Cyanoethyl Group

Abstract

The molecular motion of side chain with cyanoethyl groups in polymers having rigid and flexible main chains was investigated by dielectric measurement. Cyanoethylated polysaccharides with a rigid main chain showed a large dielectric relaxation (β) at low temperature (-50°C), β relaxation was enhanced by adding tricresylphosphate as a plasticizer. This β relaxation originates from the molecular motion of cyano group in the side chain. The β relaxation in cyanoethylated hydroxypropylcellulose, internal-plasticized cellulose, was very small and the α relaxation due glass transition was clearly observed. In cyanoethylated ployvinylalcohol and polyhydroxymethylene having a flexible main chain, the small β relaxation was observed just below each glass transition temperature (Tg). The relationship between the dielectric relaxation strength of the side chain and main chain structures was evaluated from the ratio of Tg to Ts (β relaxation temperature), corresponding to the magnitude of the chain mobility. It was revealed that cyanoethyl group connected with a rigid main chain was appropriate for a large dielectric relaxation strength in β relaxation.