Self-organization of imidazolium ionic liquids in aqueous solution

The self-organization and micelle formation of ionic liquids in aqueous solution is significant to the future use, application and environmental fate analysis of ILs. This review analyzes and summarizes the results obtained to date by a significant number of research groups on the micelle formation of imidazolium ILs in an aqueous solution, including the phenomena observed. Research in this field is often limited to authors making contributions with a small number of ILs determining their behavior in aqueous solution. This generally does not provide a broad overview of the overall surface behavior. Therefore this review was seen as necessary as to provide as complete picture as possible of the surface interactions of ILs. Imidazolium ionic liquids with alkyl chains longer than four are generally seen to behave as amphiphilic compounds, displaying interface interaction. Similarly to typical surfactants, imidazolium ionic liquids also display the characteristic chain length dependence of the interface ordering phenomena. This review indicates that there are a number of areas which require further investigation. First of all a study of more complex systems including salts, organic molecules as well as other ILs/surfactants as a result of more complicated systems which might be applied in technology. Mixtures with other surfactants may alter application of ILs in emulsion systems. Further understanding of the structural aspects of the monomer ILs effects on micellar structure and the interaction capability for various classes of molecules is needed. (C) 2008 Elsevier B.V. All rights reserved.