ASAXS Studies on SPEK Nano-Composites Containing Phosphotungstic Acid

Nano-composites based on ionomers gained importance due to the potential application as membranes for Direct Methanol Fuel Cells. Sulfonated poly(ether ketone), SPEK, has been used as polymeric matrix for such applications due to its low prize and reduced permeability to methanol. The proton-conductivity, another key factor for us ing a membrane for fuel cell, of SPEK is relatively low (when compared to commercial Nafion® membranes, for instance), therefore inorganic proton-conductors should be added in or der to facilitate the proton-transport through such membranes. In this field, a lot of work has b een done already in GKSS including the synthesis and anchoring of new heteropolyacids to the polymer backbone.(1-3) Up to now, the distribution of the heteropolyacid in the ionomer matrices has not been investigated in details. ASAXS proved to be a helpful tool in order to investigate the distribution of zirconium oxide, ZrO2, and layered zirconium phosphates (4,5). In the present report, we analyse the distribution of phosphotungstic acid, PTA, (a commercial heteropolyacid) in SPEK nano- composites by ASAXS .The preparation of the membranes is described elsewhere (1,2). The ASAXS measurements were performed at the JUSIFA beamline at HASYLAB in the energy range of the LIII absorption edge of tungsten at 10.21 keV.