Abstract: Two series of copolyesters based on p-acetoxybenzoic acid (Ac-HBA), terephthalic acid(TA) and bisphenol Adiacetate(Ac-BPA) or bisphenol Sdiacetate (Ac-BPS) were prepared by melt polycondensation technique. The copolyesters in a certain extent of compositions were thermotropic with wide liquid crystalline temperature ranges. The minimum amount of mesogenic units derived from Ac-HBAin feed necessary for the appearance of mesomorphic phase is about 10 % mol. Tgs of BPA series copolyesters were essentially constant and close to that of polymer of rigid spacer regardless of compositions. But the Tfs showed a minmum value towards the compositions.

Key words: Liquid crystalline copolyesters, Terephthalate of bisphenols as rigid Spacer, Glass transition Temperature