A series of block copolyesters based on terephthaloyl chloride
hydroquinone and hydroxy terminated telechelic polysulfone were synthesized. The copolyesters showed composition-dependent liquid crystalline properties within a wide temperature range. The mesomorphous properties were examined by visual observation of stir-opalescence
birefringence and X-ray diffraction. The minimum mole fraction of mesogenic units needed for appearance of melt anisotropy is not higher than 0.10. The glass transition temperature of the copolyesters are close to that of polymers merely of spacers.