The aggregation behavior of fluorinated surfactant in an ionic liquid

Although ionic liquids have been studied as self-assembly media, the aggregation of fluorinated surfactants in ionic liquids has not been fully understood. In this work, the aggregation behavior of the fluorinated surfactant, N-ethylperfluorooctane sulfonamide (N-EtFOSA), in the aprotic ionic liquid, 1-ethyl-3-methylimidazolium ethylsulfate ([C 2 mim][EtSO 4 ]), was studied using surface tension, 19 F-NMR, dynamic light scattering (DLS), and cryo transmission electron microscopy (cryo-TEM). The surface properties and thermodynamic parameters were calculated based on the results of surface tension measurements. It was found that the fluorinated surfactant exhibits a considerable surface activity in aprotic ionic liquids, and its critical micelle concentration (cmc) increases with increasing temperature. In addition, the surface properties indicate that solvophobic interactions are the main driving force for micelle formation. The thermodynamic parameters for micelle formation derived from the temperature dependence of the cmc revealed that micelle formation is an enthalpy-driven process. DLS and cryo-TEM results indicated the presence of nanoscale micelles in the N-EtFOSA + [C 2 mim][EtSO 4 ] system. The results of this work imply that this fluorinated surfactant exhibits a more pronounced surface activity than conventional hydrocarbon surfactants in [C 2 mim][EtSO 4 ]. The self-assembly of fluorinated surfactants in aprotic ionic liquids