Microemulsions with novel hydrophobic ionic liquids

Abstract

The phase behaviour of different ternary mixtures containing water, a hydrophobic ionic liquid (IL) and Triton X-100 have been examined as a function of surfactant concentration and temperature, maintaining equal volumes of water and IL. In all previously published studies on water–IL microemulsions the hydrophobic IL contained hexafluorophosphate (PF₆⁻) as anion. As this anion is not stable towards hydrolysis, our aim was to replace it by the hydrolysis-stable anion bis-triflimide (NTf₂⁻). The challenge was to find a suitable cation, which, in combination with the chosen anion, forms microemulsions with an efficiency equal or greater than reported values. The cation leading to the most efficient microemulsion was [ali336]⁺, which is based on the phase transfer catalyst aliquat 336. Thus the IL [ali336]NTf₂ turned out to be a suitable choice for a hydrophobic room temperature IL which forms microemulsions of efficiencies comparable to those of water–[bmim]PF₆ systems, whilst being stable towards hydrolysis.