Nanodroplet Cluster Formation in Ionic Liquid Microemulsions

A common ionic liquid (IL), 1‐butyl‐3‐methylimidazolium tetrafluoroborate (bmimBF₄), is used as polar solvent to induce the formation of a reverse bmimBF₄‐in‐toluene IL microemulsion with the aid of the nonionic surfactant Triton X‐100. The swelling process of the microemulsion droplets by increasing bmimBF₄ content is detected by dynamic light scattering (DLS), conductivity, UV/Vis spectroscopy, and freeze‐fracture transmission electron microscopy (FF–TEM). The results show that the microemulsion droplets initially formed are enlarged by the addition of bmimBF₄. However, successive addition of bmimBF₄ lead to the appearance of large‐sized microemulsion droplet clusters (200–400 nm). NMR spectroscopic analysis reveal that the special structures and properties of bmimBF₄ and Triton X‐100 together with the polar nature of toluene contribute to the formation of such self‐assemblies. These unique self‐assembled structures of IL‐based microemulsion droplet clusters may have some unusual and unique properties with a number of interesting possibilities for potential applications.