Ionic liquids as model systems for the study of the behaviour of electrolytes and surfactants in solutions

Ionic liquids are among the most studied systems in recent years, and this field is still growing considerably, focusing not only on fundamental research but also on the development of ionic liquids for specific applications. In this paper, the similarities and differences between conventional, "classical" electrolytes and common surfactants and ionic liquids, as well as the surface-active ionic liquids, are discussed to highlight their importance and point out their weaknesses. A brief review of the literature data shows that ionic liquids behave like "classical" electrolytes in solutions and can be described by existing models within the range of their validity. Models that describe concentrated electrolyte solutions well are still lacking, and here ionic liquids, which are less constrained by solubility than ordinary electrolytes, can serve as model systems. The micellization of surface-active ionic liquids in aqueous solutions can be described in the same way as for conventional surfactants, but surface-active ionic liquids offer more opportunities to study specific ion and isomer effects.