Synthesis and characterization of poly(ester‐sulfone)s

Aliphatic and aromatic‐aliphatic poly(ester‐sulfone)s were synthesized by the transesterifications of diphenyl adipate and diphenyl phthalates (ortho, meta, para) with two sulfonecontaining diols, 1,3‐bis (3‐hydroxypropylsulfonyl) propane (Diol‐333) and 1,4‐bis(3‐hydroxypropylsulfonyl) butane (Diol‐343). Based on DSC and WAXD studies, the aliphatic homopoly(ester‐sulfone)s are semicrystalline at room temperature and liquid crystalline at elevated temperature, while their copolymers with alkanediols are liquid crystalline. The liquid crystalline phase formation in aliphatic poly(ester‐sulfone)s is attributed to the strong dipole‐dipole interactions between sulfone groups. The aromatic‐aliphatic poly(estersulfone)s from diphenyl phthalate (ortho) and isophthalate (meta) are amorphous. They are soluble in trifluoroacetic acid and m‐cresol at room temperature, and DMF, DMAC, and DMSO at elevated temperature. The aromatic‐aliphatic poly(ester‐sulfone)s from diphenyl terephthalate are semicrystalline and are soluble only in trifluoroacetic acid. For a given diol, the glass transition temperatures of aromatic‐aliphatic poly(ester‐sulfone)s increase from phthalate to isophthalate to terephthalate. This is because the flexibility of the benzene ring in the polymer backbone decreases from ortho to meta to para substitution. As a comparison, polyesters without sulfone groups were synthesized from two alkanediols, 1,9‐nonanediol and 1,10‐decanediol, and the diphenyl esters. The poly(ester‐sulfone)s have glass transition temperatures 60–80°C higher than the corresponding polyesters without sulfone groups, due to the strong dipolar interactions between sulfone groups.