Facile synthesis of sulfonated poly(phenyl-alkane)s for proton exchange membrane fuel cells

Sulfonated poly (phenyl-alkane)s with all-carbon backbones exhibit excellent chemical stability; however, their applications in proton exchange membranes are limited. Herein, we report a facile synthesis of three sulfonated poly (phenyl-alkane)s SP1–SP3 via efficient acid-catalyzed Friedel−Crafts polycondensations of commercially available 2,3,4,5,6-pentafluorobenzaldehyde with three aromatic monomers, followed by mild and efficient nucleophilic substitution of para-aryl-F with sodium 4-oxybenzenesulfonate. In the characterization of the three polymers, the single-component adsorption–desorption isotherms of N2 and CO2 confirmed their intrinsic ultramicroporosity. For the SP3 membrane, small-angle X-ray scattering and atomic force microscopy measurements revealed that larger ionic clusters and smaller hydrophobic assembly domains led to better ionic channel connectivity. These features and the observed high ion exchange capacity and narrowly distributed ultramicropores synergistically determined its high conductivity. Moreover, the SP3 membrane exhibited excellent oxidative stability and good mechanical properties, enabling the successful application in H2/air proton exchange membrane fuel cells.