Ionic liquid clusters: structure, formation mechanism, and effect on the behavior of ionic liquids.

The microstructure of ionic liquids (ILs) has attracted much attention due to their relevance in physiochemical properties and behavior of ILs. The existence of clusters (or microheterogeneous structure) is one of the main features for many ILs, which provides fundamental information for understanding the performance of ILs in their applications. This perspective concentrates on the recent progresses in IL clusters research. Firstly, we give a brief introduction on the structure of clusters in neat ILs and IL solutions. Secondly, the possible formation mechanism of the IL clusters is described. Then, the effects of the clusters on the physicochemical properties, interfacial properties, confined geometry and assembly processes of ILs are discussed. Finally, we address the associated challenges and prospects on the future study of IL clusters.