Positronium formation in aromatic polymer electrolytes for fuel cells

We measured the yield of positronium (Ps) in sulfonated aromatic proton conducting membranes for the polymer electrolyte fuel cell (PEFC) with and without - SO2- in their chemical structures by positron annihilation lifetime spectroscopy (PALS). It was observed that Ps formation is almost totally inhibited in the polymers without - SO2- such as sulfonated poly(ether ether ketone) (SPEEK). On the other hand Ps favorably forms in those with - SO2- as sulfonated polyether sulfone (SPES), which is due the anti-inhibition effect of -SO2-. The high probability of Ps formation in these polymers enables the study of the free volume and the mechanism of gas permeation by PALS. © 2009 American Chemical Society.