Sulfonated polysulfone as promising membranes for polymer electrolyte fuelcells

A new, milder sulfonation process was used to produce ion-exchange polymers from a commercial polysulfone (PSU). Membranes obtained from the sulfonate d polysulfone are potential substitutes for perfluorosulfonic acid membrane s used now in polymer electrolyte fuel cells. Sulfonation levels from 20 to 50% were easily achieved by varying the content of the sulfonating agent a nd the reaction time, ion-exchange capacities from 0.5 to 1.2 mmol SO3H/g p olymer were found via elemental analysis and titration. Proton conductiviti es between 10(-6) and 10(-2) S cm(-1) were measured at room temperature. An increase in intrinsic viscosity with increasing sulfonation degree confirm s that the sulfonation process helps to preserve the polymer chain from deg radation. Thermal analysis of the sulfonated polysulfone (SPSU) samples rev eals higher glass transition temperatures and lower decomposition temperatu res with respect to the unsulfonated sample (PSU). Amorphous structures for both PSU and SPSU membranes were detected by X-ray diffraction analysis an d differential scanning calorimetry. Preliminary tests in fuel cells have s hown encouraging results in terms of cell performance. (C) 2000 John Wiley & Sons, Inc.