Role of the Surfactant Structure in the Behavior of Hydrophobic Ionic Liquids within Aqueous Micellar Solutions

Abstract

The behavior of an ionic liquid (IL) within aqueous micellar solutions is governed by its unique property to act as both an electrolyte and a cosolvent. The influence of the surfactant structure on the properties of aqueous micellar solutions of zwitterionic SB-12, nonionic Brij-35 and TX-100, and anionic sodium dodecyl sulfate (SDS) in the presence of the "hydrophobic" IL 1-butyl-3-methylimidazolium hexafluorophosphate ([bmim][PF(6)]) is assessed along with the possibility of forming oil-in-water microemulsions in which the IL acts as the "oil" phase. The solubility of [bmim][PF(6)] within aqueous micellar solutions increases with increasing surfactant concentration. In contrast to anionic SDS, the zwitterionic and nonionic surfactant solutions solubilize more [bmim][PF(6)] at higher concentrations and the average aggregate size remains almost unchanged. The formation of IL-in-water microemulsions when the concentration of [bmim][PF(6)] is above its aqueous solubility is suggested for nonionic Brij-35 and TX-100 aqueous surfactant solutions.

Influence of chemical architecture of oils and ionic liquid on the physicochemical and thermodynamic properties and microenvironment of anionic surfactant based microemulsion

“…Such studies have clearly demonstrated the effectiveness of ILs in tuning the key physicochemical properties of these systems because of their impressive solvation ability which facilitates interaction with classical surfactants and have attracted widespread attention due to the multifaceted practical uses of such systems [11][12][13][14][15][16]. Interestingly, most of these studies were involved with a conventional anionic surfactant, sodium dodecylsulphate (SDS) [14,[17][18][19][20].…”

Dielectric spectroscopy study on ionic liquid microemulsion composed of water, TX-100, and BmimPF6

“…The dc conductivity of bmimPF 6 solution σ m ranges from 0.17 S/m to 0.65 S/m. 32 A first estimation indicates that τ MW ranges from 4.2 to 1.1 ns in the IL/water phase region, which is in the same order as the relaxation time of the low-frequency relaxation. Therefore, this mechanism is possibly responsible for the low-frequency relaxation, but it cannot contribute to the high-frequency relaxation because even the slowest relaxation process involved in the high-frequency relaxation has a relaxation time of the order of 100 ps (see Table I).…”

“…It should be pointed out that, when φ w > 0.8 the water phase is saturated with bmimPF 6 (about 2.1 wt. %); therefore the dc conductivity of saturated bmimPF 6 solution (around 0.65 S/m) 32 is taken for σ m (IL/water and B.C. phases) or σ p (water/IL phase).…”

Interaction Between Ionic Liquids and Gemini Surfactant: A Detailed Investigation into the Role of Ionic Liquids in Modifying Properties of Aqueous Gemini Surfactant

“…Comprehensive studies on the interactions between mixtures of gemini and conventional single chain surfactants of different charge classes to form mixed micellar aggregates have been reported [31][32][33][34]. In recent decades, studies on the interactions between single chain surfactants and IL have been reported and the results obtained are discussed at length [35][36][37][38][39][40][41][42][43][44][45][46]. Pandey et al [35][36][37][38] reported the dual behavior of IL in aqueous solutions of single chain surfactants.…”