A block copolymer containing terephthaloyl bis(4 oxybenzoyl) (triad) mesogen and polyether sulfone (PES)unit was synthesized by polycondensation of PES oligomer. terephthaloyl dichloride and 1.6-hexene bis(-p-hydroxy-benzoate). This obtained block copolymer was added into the blends of PESPoly(ethylene terephthalate)(PET)/Poly(-p- hydroxybenzoic acid)(PHB). Comparing the Tg and phase morphology of the blends with different component of the block copolymer
it was shown that this block copolymer could improve the compatibility of PES-PET/PHB.