Room temperature ionic liquid (DMOImTf) based upon 2,3-dimethyl-1-octylimidazolium cation and trifluoromethanesulfonate or triflate (CF(3)SO(3))(-) anion has been synthesized and shows conductivity of 5.68 mS/cm and viscosity of 26.4 cP at 25 degrees C. Ion conducting polymer electrolytes based on polymers (poly(ethylene oxide) (PEO) and polyvinylidenefluoride-co-hexafluoropropylene (PVdF-HFP)) and ionic liquid (DMOImTf) were prepared in film form by the casting technique. The conductivity of polymer electrolytes containing 0.5 M LiCF(3)SO(3) in PEO:DMOImTf taken in equal weight ratio increases with the addition of propylene carbonate (PC) while its mechanical stability improved by dispersing nanosize fumed silica. However, polymer electrolytes containing PVdF-HFP and ionic liquid show a high value of conductivity (10(-4)-10(-3) S/cm) alongwith better mechanical stability.

The morphology of proton conducting membranes based on sulfonated poly(aryl ether ketone) (SPAEK-6F) and recast Nafion membranes containing hydrophilic/hydrophobic ionic liquids has been investigated by small-angle X-ray scattering (SAXS) and tapping mode atomic force microscopy (TM-AFM). The hydrophilic/hydrophobic nature of the ionic liquid has been found to affect the morphology, conductivity and thermal stability of the membranes. The small angle upturn in scattering intensity at very low angles observed in SAXS for different membranes suggests the presence of large scale fluctuations, whereas the absence of ionomer peak for membranes based on SPAEK-6F is possibly due to the higher rigidity of hydrophobic part of the polymer despite the presence of ionic domains. The correlation between morphology and properties of different membranes containing ionic liquids will be helpful in improving the design of proton conducting membranes containing ionic liquids for applications in polymer electrolyte fuel cells (PEFCs) at medium (100-200 °C) temperatures and under anhydrous conditions.

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