Synthesis and characterization of sulfonated cardo based poly(arylene ether sulfone) multiblock copolymers for proton exchange membrane

Sulfonated multiblock poly(arylene ether sulfone) copolymers (SMPESs) containing phenolphthalein anilide (PPA) as a cardo group were prepared from the precursors of hydrophilic and hydrophobic block oligomers. The hydrophobic oligomer was prepared by 4,4′-dihydroxydiphenylsulfone and 4,4′-dichlorodiphenylsulfone. On the other hand, hydrophilic oligomer prepared by disodium-3,3′-disulfonate-4,4′-dichlorodiphenylsulfone (SDCDPS) and PPA. Post-sulfonation process was applied to add sulfonic acid group on PPA unit of MPES copolymers by using concentrated sulfuric acid. Sulfonated multiblock copolymers (SMPESs) with hydrophilic units of 15, 20 and 25 mol% were successfully synthesized by varying the different mole ratios to control the degree of sulfonation. SMPESs were studied by FT-IR, 1H-NMR spectroscopy, and thermo gravimetric analysis (TGA). Sorption experiment resulted the water uptake of SMPESs that was 16%–62% at 80 °C. The resulted ion exchange capacities (IEC) were 1.14–1.78 (meq/g), and proton conductivities were 65–93 (mS/cm) evaluated as increasing IEC by altering the temperature and relative humidity (RH).