Structural investigation of polystyrene grafted and sulfonated poly(tetrafluoroethylene) membranes

Structural investigation of polystyrene grafted and sulfonated poly(tetrafl uoroethylene) (PTFE) membranes prepared by radiation-induced grafting of st yrene onto commercial PTFE films and subsequent sulfonation was carried out by differential scanning calorimetry and X-ray diffraction. The effect of the structural changes taking place in the membranes during the preparation procedure (grafting and sulfonation) and the variation of the degree of gr afting on melting temperature (T-m), glass transition temperature (T-g), he at of melting (DeltaH(m)), and degree of crystallinity was studied. The mel ting temperature (T-m) was found to be independent of the degree of graftin g unlike glass transition temperature (T-g), which was found to be a functi on of the degree of grafting. Moreover, the degree of crystallinity of the membranes was found to decrease with the increase in the degree of grafting . The results of this work suggest that grafting takes place in the entire amorphous region without any significant disruption in the crystalline stru cture of PTFE Elm and the decrease in the degree of crystallinity is mainly attributed to the dilution effect. (C) 2001 Elsevier Science Ltd. All righ ts reserved.