Sulfonated polystyrene/PTFE composite membranes

This paper describes the preparation and characterization of sulfonated polystyrene (SPS)/polytetrafluoroethylene (PTFE) composite membranes for direct methanol fuel cells (DMFCs). The SPS/PTFE composite membranes were prepared by adjusting the ratio of styrene/divinylbenzene (DVB) in reaction mixtures that were impregnated in porous PTFE substrate membranes. The soaked substrates were then thermally polymerized and sulfonated with chlorosulfonic acid. SEM and ATR-FT-IR observations confirmed that the porous PTFE substrates were filled successfully with SPS. The water content, IEC values, the methanol permeability, and the ion conductivity increased with increasing ratio of styrene/DVB in the sulfonated membranes. The composite membranes showed comparable, or higher ion conductivity and lower methanol permeability than Nafion®117 membrane, indicating that the composite membranes could be an alternative membrane for DMFCs.