ON THE SOLUTION CHARACTERIZATION OF AN ALL-AROMATIC LIQUID-CRYSTALLINE COPOLYESTER

Solution characterization of the thermotropic liquid-crystalline copolyester synthesized from terephthalic acid, phenyl hydroquinone, and (1-phenylethyl) hydroquinone (2 : 1 : 1) has been performed. Viscometry, size exclusion chromatography, and light scattering have been carried out under the optimal conditions found for measurement: 85-degrees-C in a 50/50 mixture by weight of phenol/1,2,4-trichlorobenzene. The absolute weight-average molecular weight from light-scattering measurements served for calibration of indirect methods of characterization (e.g., the limiting viscosity number [eta] is related to the molecular weight by [eta] = 5.10 x 10(-4) M(w)0.72), and the molecular weight per unit chain length, M(L)BAR*, from light scattering and size exclusion chromatography (SEC) is found to be 28 angstrom-1, consistent with theoretical expectations. The calculated persistence length q is 28 angstrom. Moreover, the methodology of SEC characterization enables the kinetics of solid-state postpolymerization of this liquid-crystalline copolyester to be studied. (C) 1993 John Wiley & Sons, Inc.