Synthesis and characterization of sulfonated poly(arylene ether sulfone) ionomers incorporating perfluorohexylene units for DMFC membranes

A new, sulfonated poly(arylene ether sulfone) ionomer with partially fluorinated groups (F-SPAES) was synthesized by the direct polymerization of 1,6-bis(4-fluororphenyl)-perfluorohexane (FPPFH) and 6F-bisphenol A (6F-BPA) with 3,3′-disulfonated 4,4′-difluorodiphenyl sulfone (SDFDPS). The effect of fluorination on the membrane properties and membrane-electrode assembly (MEA) performance for DMFC applications were investigated comprehensively and compared with the pristine SPAES sample. Deliberate control of the hydrophobicity as well as the degree of sulfonation in the F-SPAES membranes allows the effective suppression of water uptake and methanol permeability, while barely affecting the proton conductivity and IEC value. Such an improvement in the membrane properties contributes to the superior single cell performance of the F-SPAES compared to pristine SPAES and Nafion®.