The preparation and characterization of nanoscale metal sulfide particles i
n perfluorinated ionomer membranes, including Nafion and those based on the
sulfonimide ionomer and the bis(sulfonyl)methane ionomer, are reported. Th
e results suggest that these membrane films all contain hydrophilic structu
ral cavities and that the nanoscopic structures of the sulfonimide ionomer
and bis(sulfonyl)methane ionomer membranes are quite similar to that of the
commercial Nafion film. Properties of the nanoscale particles in the ionom
er membranes are presented, and their implications for the understanding of
membrane nanoscopic structural details are discussed.