PHASE AND RELAXATION TRANSITIONS OF THERM OTROPIC LIQUID-CRYSTALLINE COPOLYESTER ULTRAX

Phase and relaxation transitions in the commercial thermotropic LC cop olyesters (trade marks Ultrax 4002 and Ultrax 4003) with different rat ios between the components in macromolecules were studied by the metho ds of X-ray analysis, differential scanning calorimetry, and mechanica l relaxation spectroscopy. Even though the two copolymers studied have only a slight difference in composition, their structures and the tem perature dependences of their properties appear to be quite different. In particular, the of freshly formed fibers samples show a two-fold d ifference in the maximum degree of crystallinity upon annealing. The t wo materials are characterized by quite different crystal structures a nd abilities to crystallization. It was found that the glass transitio n temperature of two Ultrax copolyesters, as determined by activation of the mobility of the most rigid structural units, is independent of the composition and is equal to similar to 125 degrees C. The annealed copolyesters are two-phase systems, in which the crystalline phase co exists with an LC phase having an unusual structure. The latter phase is characterized by aperiodic spatial arrangement of smectic layers. O n heating, the crystalline phase of copolyester exhibits transition to a pseudohexagonal mesophase.