Preparation and characterization of a proton‐exchange membrane by the radiation grafting of styrene onto polytetrafluoroethylene films

Radiation‐induced simultaneous grafting of styrene onto polytetrafluoroethylene (PTFE) films and the subsequent sulfonation in the chlorosulfonic acid/dichloroethane were investigated. The effects of the main radiation grafting conditions, such as the type of solvents, irradiation dose, dose rate, the styrene concentrations, etc. , on the degree of grafting (DOG) were studied. To elucidate the influence of both the grafting and sulfonation conditions on the properties of the PTFE‐ g ‐polystyrene‐sulfonic acid (PSSA) membranes, the sulfonation conditions, including the sulfonation temperature and the concentration of the ClSO 3 H with respect to the DOG, were systematically evaluated. The grafted and sulfonated membranes were characterized by FTIR–ATR spectra, ion‐exchange capacity (IEC), water uptake, thickness measurement, etc. The as‐prepared PTFE‐ g ‐PSSA membranes in this work showed a good combination of a high IEC (0.85–2.75 meq g −1 ), acceptable water uptake (8.86–56.9 wt %), low thickness, and volume expansion and/or contraction. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1415–1428, 2006