STRUCTURAL EVOLUTION OF LC POLYMERS AND T HEIR BLENDS

In order to understand heat-mediated evolution of the structure and rh eological properties of thermotropic LC polymers, we examined a series of chemically similar homopolyesters, random copolyesters, and their blends using rheological measurements, X-ray diffraction analysis, dif ferential scanning calorimetry, and mechanical testing. It was found t hat the examined polymers exhibit a complex sequence of temperature-in duced relaxation and phase transitions, resulting in conformationally disturbed ordered phases. Copolyesters were found to exhibit a greater -tendency to form multiple-ordered phases (which melt separately as th e temperature increases) than the homopolyesters. For the copolyester based on p-hydroxybenzoic acid, terephthalic acid and phenylhydroquino ne, we suggested the existence of the LC smectic A mesophase; this is quite uncommon for this polymer, which shows no alternation of mesogen ic groups in the main chain, although alternation was known to be a ne cessary prerequisite for the occurrence of a layer structure.