Block copolymers witBl poly(tetrametnylene glycol)(PTMG) or poly(ethylene glycol)(PEG) spacers of different length and tile 4,4'-(terephthaloyldioxy) dibenzoyl unit have been synthesised by interfacial polymerization. Thermal properties were found to be dependent on average length of hard segment as well as of the polyether segment. All copolyesters were elastomeric at room temperature. Thermtopic liquid crystalline behavior was found for all block copolyester and orginated from the hard segment.