Effects of 1-Alkyl-(and 1-Benzyl)-2,3-Dimethylimidazolium Ionic Liquids as Additives on the Micellar Behavior of Surfactant SB-12

The micellization and surface-active behavior of zwitterionic surfactant N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulfonate (SB-12) in aqueous media were investigated in the absence and presence of different alkyl-appended and benzyl-appended ionic liquids (IL) 1-butyl-2,3-dimethylimidazolium chloride bdmim]Cl], 1-butyl-2,3-dimethylimidazolium bromide bdmim]Br], 1-hexyl-2,3-dimethylimidazolium bromide hdmim]Br], and 1-benzyl-2,3-dimethylimidazolium chloride bzdmim]Cl]. The characteristics of self-organization processes in SB-12 + IL/water systems include critical micelle concentration (cmc), aggregation number (N_agg), micellar size (D), surface, and adsorption parameters. These parameters were determined by the fluorescence and surface tension measurements. In SB-12 solutions, cmc were found to be decreasing to different extents in the presence of all the studied IL than in pure water. The addition of IL hdmim]Br] decreases the cmc of aqueous SB-12 to rather a low extent. The other three IL show a prominent lowering in cmc of surfactant SB-12 to different magnitude. The maximum lowering in cmc was observed due to addition of benzyl-appended IL bzdmim]Cl]. The aggregation number of aqueous SB-12 solution obtained in general is higher at high wt.% of added IL. The average micellar size was also found to increase upon addition of IL. Both IL anions and cations interacted with the charged centers present on the zwitterionic surfactant SB-12, which caused a substantial increase in the surface activity.