Comparison of the Properties of Thermotropic Liquid Crystalline Copolyesters Containing Different Dissymmetrical Units.

摘要

The effect of dissymetrical units on the properties of thermotropic liquid crystalline copolyesters based on hydroxybenzoic acid (HBA), terephthalic acid (TPA), and poly (ethylene terephthalate) (PET) units was examined. The dissymmetrical units employed included 2,7-dihydroxynaphthalene (2,7-DHN), 1,4-dihydroxynaphthalene (1,4-DHN), and bromo-hydroquinone (Br-HQ). All of these polymers exhibited turbid melts. The flexible PET units lower the melting and/or stick temperature, and between 10 to 20 mol % is a critical level to achieve values in the range of 250 C or lower. The copolyesters based on 2,7-DHN have the highest glass transition temperatures and maintain stiffness to the highest temperatures.