Regulation of anionic structure and CO2 on the vesicle formation of imidazolium-based ionic liquids in water

The understanding of vesicle formation mechanism of ionic liquids (ILs) in aqueous solution is of great significance for the innovation and application of IL vesicles. In this work, a series of single-tailed amphiphilic ionic liquids (ILs) consisted of 1-tetradecyl-3-methylimidazolium [C14mim]+ and five kinds of anions have been designed to examine the regulation of anionic structures on the vesicle formation of ILs in water without any additives by surface tension, conductivity, cryogenic transmission electron microscopy, dynamic light scattering, small-angle X-ray scattering, and NMR spectroscopy. It is found that synergistic effect of hydrophobic and π-π interaction plays a vital role in the vesicle formation of 1-tetradecyl-3-methylimidazolium 1, 2, 3-benztriazole ([C14mim][1, 2, 3-Ben]). Interestingly, reversible structural transition between vesicle and micelle of this IL is observed by alternating CO2 and N2 bubbling due to the reversible formation of carbamate arising from the reaction between CO2 and the anion of the IL.