KINETICS OF MESOPHASE TRANSITIONS IN THERMOTROPIC COPOLYESTERS .3. POLY[(PHENYL-P-PHENYLENE TEREPHTHALATE)-CO-[(1-PHENYLETHYL)-P-PHENYLENE TEREPHTHALATE]] COPOLYESTER

Structure formation kinetics of a copolyester consisting of p-benzenedicarboxylic acid (TPA), phenylhydroquinone (PHQ), and (l-phenylethyl)hydroquinone (PEHQ) with a molar ratio of 50/25/25 has been studied. This copolyester shows periodic c-axis order in its X-ray diffraction pattern due to equal unit lengths of the comonomers. The crystal unit cells for quenched and annealed TPA/PHQ/PEHQ copolyester are both monoclinic but with slightly different sizes. Two transition processes from its nematic to solid states can also be identified. Isothermal kinetics of the transitions indicate that the fast transition process is nucleation-controlled crystal growth. The development of the slow process is hampered by the previously grown crystals in the fast process. A higher transition temperature of the fast transition process compared with that of the slow process is attributed to a larger enthalpy change (thermodynamic effect) and melting of relatively ordered domains (kinetic effect) during this transition. © 1990, American Chemical Society. All rights reserved.