synthesis and characterization of novel poly(ether sulfone)s copolymers bearing pendant carboxyl groups

Aromatic poly(ether sulfone)s (PESs) are engineering thermoplastic materials with excellent chemical and thermal stability. Despite this, PESs have some limitations. Lack of hydrophilic groups and the closing arrangement of macromolecular chains lead to the high hydrophobicity of PES, causing the accumulation phenomena on the surface of membranes (biofouling). With the aim to obtain materials well balanced in terms of hydrophobic and hydrophilic character, the insertion of carboxyl and sulfonic groups and their effects on the behaviors of the polymers was verified and applied to the engineering of different kind of membranes for several applications. New functionalized Poly(ether sulfone)s having different molar ratio of 4,4-bis phenoxy pentanoic acid (diphenolic acid; DPA) units were synthesized and structurally characterized by (1H and 13C)-NMR, MALDI-TOF MS, FT-IR, DSC, and Contact Angle analyses. Thermal degradation processes were also studied by direct-pyrolysis/MS (DPMS), stepwise pyrolysis-gas chromatography/MS and thermogravimetric techniques. The presence of different amount of DPA units along the polymer chains affects the chemical and physical properties of the copolymers. The Tg and the contact angle values decrease as the molar fraction of DPA units increases, whereas the hydrophilicity increases. NMR and MALDI-TOF MS analyses show that all polymer chains are, as expected, randomic and almost terminated with hydroxyl and chlorine as end groups. The thermal stabilities, the pyrolysis products and the thermal degradation mechanisms of the copolymer samples have been identified through the combination of DPMS, Py-GC/MS and TGA data. Their thermal behavior was compared with that of a well-known commercial PES (referred to as PESES) sample.