Ionic liquids composed of linear amphiphilic anions: Synthesis, physicochemical characterization, hydrophilicity and interaction with carbon dioxide

Development of new task-specific ionic liquids (ILs) constitutes an important goal in chemistry and chemical technology. We hereby report four surface active ILs (SAILs) composed of the well-known cations (1-butyl-3-methylimidazolium [bmim+], tetrabutylammonium [TBA+]) and long-alkyl-chain anions (lauryl sulfate [C12SO4−], lauryl ether sulfate [C12ESO4−]). Thermal stabilities, viscosities, interactions with water and polarized optical microscopy (POM) were investigated suggesting that new SAILs are highly viscous and thermally stable until 180 °C. [bmim][C12SO4], [bmim][C12ESO4] and [TBA][C12ESO4] are miscible with water, whereas [TBA][C12SO4] is immiscible. Ab initio calculations were employed to characterize hydrophilicity/hydrophobicity balance of all four compounds, the results being in concordance with our experimental observations. [bmim][C12SO4] and [bmim][C12ESO4] normally exhibit non-Newtonian behaviors and form liquid crystals (LCs) with water, but [TBA][C12SO4] and [TBA][C12ESO4] are Newtonian liquids. Using semiempirical molecular dynamics simulations, we show that the sulfate group of the synthesized SAILs exhibits certain potential to capture dissolved CO2.