Surface investigations of radiation grafted FEP-g-polystyrene sulfonic acid membranes using XPS

X-ray photoelectron spectroscopy (XPS) investigations of FEP-g-polystyrene sulfonic acid membranes prepared by radiation-induced graft copolymerizatio n of styrene onto poly(tetrafluoroethylene-co-hexafluoropropylene), FEP fil ms were conducted to monitor the morphological changes accompanied the memb rane two-step preparation procedure and the Variation of the degree of graf ting. The spectra of XPS were analyzed with the main focus on carbon, fluor ine, sulfur, and oxygen as they compose the basic elemental components of t he membrane. The original FEP film was found to undergo structural changes in terms of chemical composition under the influence of grafting and sulfon ation. The surface of the the resulting membranes was found to have a nearl y pure sulfonated hydrocarbon structure. The atomic ratio of F/C in the mem branes was found to be strongly dependent on the degree of grafting whereas , the binding energies of the elemental components of the membranes were fo und to be independent of the degree of grafting. The results of this study suggest that surface structural properties play a signification part in the degradation of radiation-grafted membranes.