Surface-active ionic liquids: A review

The combination of water and surface-active ionic liquids provides a unique reaction medium, facilitating aggregation and micellization of the ionic liquid to allow for chemical reactions in bulk water. With a growing focus on sustainable technologies, ionic liquids have emerged as tunable solvents for multiple applications but are often too viscous or expensive for use as bulk solvent. As a result, there has been a tremendous increase in interest in the behavior of ionic liquids in the presence of water. It has already been shown that certain ionic liquids act as surfactants in aqueous solutions, enabling the combination of both solvents to afford solvent systems with unique properties. Ultimately, surface-active ionic liquids in water give rise to distinct chemistry of their own compared to traditional molecular solvents, and thus their use is rapidly growing. In this review, the general structure of surface-active ionic liquids and the key features that allow aggregation in water to give micellar structures is discussed. Furthermore, characterization techniques of the formed micelles are presented, discussing aggregation and possible methods of studying micellization behavior. Finally, current applications of surface-active ionic liquids across all fields of chemistry, from traditional organic chemistry to nanoparticle synthesis are presented. (C) 2021 The Authors. Published by Elsevier B.V.