The syntheses and characterizations of poly[oxy(2-methyl-1,3-phenylene) oxyisophthaloyl-b-oxy (2-methyl-1,3-phenylene)oxy-terephthaloyl] and the corresponding homopolymers are described. The synthesis involves the coupling of dihydroxy-terminated homo-polymers with terephthaloyl chloride. The resulting block copoly-ester was characterized by infrared spectroscopy, proton and carbon- 13 nuclear magnetic resonance spectroscopy, solution viscosity, differential scanning calorimetry, and thermogravimetric analysis.