Radiolytic preparation of poly(styrene sulfonic acid) - grafted poly(tetrafluoroethylene-co-perfluorovinyl vinyl ether) membranes with highly cross-linked networks

In this study, various amounts of a divinylbenzene (DVB) cross-linking agent (5∼30%) were introduced during a simultaneous irradiation grafting of styrene onto a PFA film of a 25 μm thickness in order to prepare a series of poly(styrene sulfonic acid)-grafted poly(tetrafluoroethylene-co-perfluorovinyl vinyl ether) (PFA) membranes with various degrees of cross-linking and grafting (29∼74%). The effects of the DVB cross-linking agent on the properties of the prepared membranes, such as water uptake, proton conductivity, methanol permeability, and chemical stability, were also investigated in this study. The results indicated that the ion exchange capacity (IEC) slightly decreased with increasing DVB content, whereas the water uptake, proton conductivity, and methanol permeability of the membrane greatly decreased. The chemical stability of the prepared membranes was found to be significantly improved with increasing DVB content. The results indicated that the cross-linked network membranes are promising for application in a direct methanol fuel cell.