THE EFFECT OF SOLVENT AND HEAT-TREATMENT ON DIELECTRIC-RELAXATION IN POLY(ACRYLONITRILE)

The relaxation of dipole polarization in films of poly(acrylonitrile) prepared by anionic and radical polymerization is studied at frequenci es from 1 to 100 kHz and at temperatures from 20 to 300-degrees-C. Two ranges of dielectric absorption are observed (near 100 and 210 - 250- degrees-C), whose parameters depend on the heat treatment and the pres ence of solvent. The first range is associated with the segmental moti on of macromolecules without intramolecular conjugation and whose nitr ile groups do not complex with the solvent. The second peak of dielect ric loss is observed at temperatures corresponding to fast conjugation reactions of the nitrile groups. This peak may be due either to the m obility of the chain segments containing a large amount of intramolecu lar rings or to a decrease in ionic conductivity because of the format ion of a three-dimensional molecular structure. Both of the processes of dielectric absorption completely disappear after heating the sample s to 230 - 250-degrees-C, which may be attributed to intramolecular cy clization (near 100-degrees-C) and the formation of a three-dimensiona l network.