Theoretical studies on the proton dissociation and degradation of sulfonated polyethylene electrolyte membrane

Proton dissociation property and chemical stability of precisely sulfonated polyethylene, p21SA, has been investigated by theoretical calculations. The results show that proton in model compound is spontaneously dissociated when hydration number is 3, while in a folded structure, only required a hydration number of 2.5, lower than Nafion. Evidently, its good proton dissociation property and folded structure are contributed to the outstanding proton conductivity of p21SA. The chemical stability of p21SA membrane is evaluated by the bond dissociation energy and chemical degradation mechanism calculations, which discloses that C–S bond is the weakest for p21SA backbone. The most favorable degradation routes are H atom abstraction by radicals followed by C–S bond scission. We hope this work can provide some ideas for the performance improvement of p21SA membrane analogues used in proton electrolyte membrane fuel cells.