Sulfonation mechanisms of aromatic polymers for PEMFC applications

Abstract

AbstractThe sulfonated aromatic polymers are competitive proton conducting materials for proton exchange membrane fuel cells because of their relatively low costs and adequate performances compared with the perfluorinated sulfonic acid ionomers. These polymeric materials can be economically synthesized by the sulfonation of existing aromatic polymers; however, the inadequate sulfonation degree has prevented the further optimization of their overall performances. In order to improve the overall performances of sulfonated aromatic polymeric proton conducting materials, the sulfonation mechanisms of typical aromatic polymers, including bisphenol A type polysulfone (BPA‐PSF), 4,4’‐biphenol type polysulfone (44BP‐PSF), poly(ether ether ketone) (PEEK), and poly(ether sulfone) (PES), are studied in terms of transition states and activation energies using density functional theory calculations with satisfactory results. It is concluded that the sulfonations are favored at the ortho‐position of direct arylene‐arylene linkage and ether bond linkage, but retarded by the bulky sulfonyl linkage, dimethyl methylene linkage, and carbonyl linkage. It is also concluded that the solvation effect from polar solvent reduces the activation barrier more efficiently than that from nonpolar solvent.