ON THE MELTING BEHAVIOR OF A THERMOTROPIC RIGID RANDOM COPOLYESTER BASED ON TEREPHTHALIC ACID AND SUBSTITUTED HYDROQUINONES

Thermotropic liquid crystalline random copolyesters, based on terephthalic acid and substituted hydroquinones, display an unusually large heat for the crystal‐nematic transition; this phenomenon is related to their highly ordered structures. To modify the structures, annealing was carried out in the solid state at different temperatures over different times. As the annealing time or temperature is increased, the melting peaks shift to higher temperatures, whereas the heat of fusion shows no significant change or is lowered, respectively. An explanation is offered in terms of crystal perfection and a molecular weight increase. No evidence for a random‐to‐block conversion on annealing is found. Copyright © 1990 John Wiley & Sons, Inc.