Two kinds of liquid crystalline copolymers

based on p-hydroxybenzoic acid

terephthalic acid and diphenols

with regular or irregular sequence structure were synthesized by melt transe-sterification or Schottern-Baumann polycondensation. Polarizing microscope

DSC and X-ray diffraction were applied to investigate influence of sequence structure on mesogen

phase transition and solid structure of the polymers. It was found that sequence structure of liquid crystalline copolyesters has a strong influence on phase transition.Generally melting temperature of irregular copolyesters is depressed compared with their regular isomers

While the typeof mesogen remains unchanged

both are thermotropic nematic phase. The solid structure of the copolyesters can be explained on thebasis of structurl unit similarity.