Free-standing anion-exchange PEO-SiO2 hybrid membranes

Free-standing anion-exchange polyethylene oxide (PEO)-SiO2 hybrid membranes with higher flexibility and good mechanical strength (tensile strength (TS) as high as 20.55 MPa) as well as high temperature tolerance (thermal degradation temperature in air, T-d, in the range of 220-240 degrees C) were prepared through sol-gel reaction of different precursors: charged alkoxysilane-functionalized PEO-1000 (PEO-[Si(OCH3)(3)](2)(+)), N-triethoxysilylpropyl-N,N,N-trimethylammonium iodine (A-1100(+)), monophenyltriethoxysilane (EPh) and in some cases also tetraethoxysilane (TEOS). Properties of the hybrid membranes, such as the thermal stability, tensile properties, hydrophilicity, and electrical performances, can be controlled by changing the feed ratio of the different sol-gel precursors. The results showed that some of the membranes have relatively good conductivity (similar to 0.003 S/cm) and so may find potential applications in alkaline membrane fuel cells. (c) 2007 Elsevier B.V. All rights reserved.