Em. Antipov et al., PHASE AND RELAXATION TRANSITIONS IN LIQUI D-CRYSTALLINE COPOLYESTER, Vysokomolekularnye soedinenia. Seria A, 36(9), 1994, pp. 1512-1528
Phase and relaxation transitions in ternary thermotropic LC copolyeste
r were studied in a wide temperature range by means of dynamic mechani
cal relaxation, DSC, and X-ray analysis. Highly oriented fibers based
on copolyester containing 45 mol% terephthalic acid, 45 mol% phenylhyd
roquinone, and 10 mol% n-hydroxybenzoic acid were used. The properties
of both as-spun fibers and fibers annealed at high temperatures for a
long time were characterized. The appearance of the mobility of the m
ost rigid structural unit in the copolyester studied was shown to resu
lt in cooperative motion of chain fragments and to control glass trans
ition temperature, which was equal to 180-degrees-C. Above this temper
ature, the transition from the initial mesomorphic structure (LC smect
ic B type) in the as-spun copolyester fibers into the nematic LC phase
was observed, and copolyester gained the ability to flow. Crystalliza
tion in the copolyester samples induced by annealing at temperatures a
bove 250-degrees-C involved the formation of two crystalline phases wi
th rhombic structure, which were characterized by different parameters
of unit cell. The maximal crystallinity of the samples did not exceed
35 - 40%. Melting of the crystalline phases was observed at temperatu
res above 300-degrees-C, and this process was shown to be accompanied
by the formation of oriented nematic melt, which became isotropic abov
e 400-degrees-C.