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-induce d graft copolymerization of styrene onto poly(tetrafluoroethylene-co-hexafluoropropylene), FEP films were conducted to monitor th e morphological changes accompanied the membrane two-step preparation procedure and variation of the degree of grafting. The spectra of XPS wer e analyzed with the main focus on carbon, fluorine, sulfur, and oxygen spectra as they compose the basic elemental components of the membr ane. The original FEP film was found to undergo structural changes in terms of chemical composition under the influence of grafting and sulfonation. The surface of the resulting membranes was found to have a nearly pure sulfonated hydrocarbon structure. The atomic ratio of F/C in the membranes was found to be strongly dependent on the degree of grafting whereas, the binding energies of the elemental components of the m embranes were found to be independent of the degree of grafting. The results of this study suggest that surface structural properties play a signification part in