DIELECTRIC-RELAXATION OF RIGID-CHAIN THER MOTROPIC LC POLYMERS STUDIES BY THE METHODS OF DIELECTRIC LOSSES AND THERMOSTIMULATED DEPOLARIZATION CURRENT

Relaxation transitions in a copolyester of p-hydroxybenzoic acid and P ET (PEE-1) and a copolyester of p-hydroxybenzoic and 2,6-hydroxynaphth oic acids (PEE-2) were studied by the methods of dielectric relaxation and thermostimulated depolarization current in a wide range of freque ncies and temperatures. Earlier unknown transitions at high and low te mperatures were revealed, and their relation to the structure and stru ctural peculiarities of LC polymers was considered. High-temperature t ransitions at 170-190 degrees C (at a frequency of 1 Hz) were explaine d by the processes of glass transition (PEE-1) as well as by their sup erposition with polymorphic transitions (PEE-2). At temperatures above the principal glass transition temperature, PEE-1 was shown to posses s a higher molecular mobility as compared to PEE-2. The hindered rotat ional mobility of PEE-2 was preserved up to temperatures close to the melting temperature T-m of the crystalline regions of polymer.