A new type of microemulsion consisting of two halogen-free ionic liquids and one oil component

A ternary system consisting of toluene, as oil phase, and two ionic liquids, i.e., 1-butyl-3-methylimidazolium octylsulfate (bmimOctOSO3) and 1-ethyl-3-methylimidazolium ethylsulfate (emimEtOSO3), has been investigated.The isotropic phase region was studied by means of conductometric, cyclic voltammetric and rheological measurements. The results show that microemulsions can be formed, where the bmimOctOSO3 take over the role of a surfactant in the spontaneous interfacial film formation process. Changes in the droplet–droplet exchange process can be assigned to transitions in the microstructure of the system from the IL-in-oil to oil-in-IL microemulsions, passing a bicontinuous phase. In the region between 5 wt.% and 21 wt.% of emimEtOSO3, reverse microemulsions with a droplet size of 2–10 nm were detected using Dynamic Light Scattering (DLS) and Cryo-Scanning Electron Microscopy (Cryo-SEM).

Phase diagram showing the two phase region as well as the different isotropic phase regions, i.e., Il/oil, bicontinuous, and oil/IL microemulsions.Figure optionsDownload as PowerPoint slide