Effect of pendant group containing fluorine on the properties of sulfonated poly(arylene ether sulfone)s as proton exchange membrane

Abstract

Three kinds of sulfonated poly(arylene ether sulfone) (xF-SPAES-40) were synthesized to explore the influence of the hydrophobic moieties on the copolymers as proton exchange membrane. Three bisphenol monomers containing different content of fluorine were reacted with 3,3′-disulfonate-4,4′-dichlorodiphenylsulfone and 4,4′-dichlorodiphenylsulfone to form xF-SPAES-40 polymers, respectively. The chemical structure of xF-SPAES-40 polymers was identified using 1H Nuclear magnetic resonance spectroscopy and Fourier transform infrared spectroscopy. The phase morphology of the obtained membranes was confirmed by small-angle X-ray scattering (SAXS) and atomic force microscopy (AFM). The properties of these sulfonated polymers towards application as a proton exchange membrane were evaluated. The morphological analysis of AFM and SAXS revealed that introduction of fluorine to the pendant group promotes microphase separation. When compared with 0F-SPAES-40, the 1F-SPAES-40 exhibited the best oxidative stability and dimensional stability at 30–90 °C. The 2F-SPAES-40 showed the highest proton conductivity among them. These results indicated that the hydrophobic components of SPAES including optimal content of fluorine were in favor of promoting proton conductivities, oxidative stability, and restraining water swelling.