The self-assembly of ionic liquids surfactants in ethanolammonium nitrate ionic liquid

Abstract

Self-assembly of ionic liquids (ILs) surfactants in ILs solvents is important from the viewpoint of both scientific research and practical application because of the advantages of high ionic nature and possible application at high temperature. In this work, the aggregation behavior of long-chain ionic liquids 1-alkyl-3-methylimidazolium chloride [Cnmim]Cl (n = 12, 14, 16) and N-alkyl-N,N-dimethylethanolammonium [CnDMEA]Cl (n = 12, 14, 16) in a protic ionic liquid, ethanolammonium nitrate (EOAN), is investigated by surface tension measurements. The variation of micellization parameters with alkyl chain length and head group type of the ILs surfactants is analyzed and compared with that in water and in ethylammonium nitrate (EAN). It is found that the critical micelle concentration (cmc) values of the IL surfactants, such as [C12mim]Cl, in EOAN are 27 times smaller than those in EAN, and 4 times smaller than those in water. This suggests that EOAN is a better self-assembly medium for the ILs surfactants. It is also found that the contribution of head groups of the ILs surfactants to the cmc values is different in EOAN, water and EAN, while the contribution of CH2 group in the alkyl chain of the ILs surfactants is generally independent of the solvents nature.