Aggregation Behavior of a Fluorinated Surfactant in 1-Butyl-3-methylimidazolium Ionic Liquids

Abstract

The aggregation behavior of a fluorinated surfactant (FC-4) was studied by surface tension measurements in 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF 4]) and hexafluorophosphate ([bmim][PF 6]) at various temperatures. A series of surface properties, including adsorption efficiency (p C 20), effectiveness of surface tension reduction (Pi CAC), maximum surface excess concentration (Gamma max) and minimum surface area/molecule (A(min)) at the air-water interface were estimated. By comparing the fluorinated surfactant with traditional surfactants, we deduced that the surface activity of the fluorinated surfactant in ILs was superior to the activity of other surfactants. From the CAC values and their temperature dependence, we estimated the thermodynamic parameters of aggregate formation. The thermodynamic parameters indicate that the aggregate of FC-4 in [bmim][BF 4] is a traditional micelle, while the aggregate of FC-4 in [bmim][PF 6] is nanodroplets composed of FC-4 molecules segregated from the solution phase. These results were further confirmed by (1)H NMR measurements.

Effect of hydrophilic ionic liquid on the micellar properties of aqueous Tween-20

“…The micelle formation of surfactants in ILs has been currently studied by many research groups [5][6][7][8][9][10][11][12][13][14][15][16]. The most frequently used ILs in this field are imidazolium salts with different anion species because of their widespread industrial use [5,9,12].…”

Micelle formation of polyoxyethylene-type nonionic surfactants in bmimBF4 studied by 1H NMR and dynamic light-scattering

“…In addition, the aggregates formed from amphiphilic compounds would be able to solubilize substances essentially insoluble in ionic liquids, which must widen the application fields of ionic liquids. From these points of view, the micelle formation of surfactants in ionic liquids has been currently studied by many research groups [9][10][11][12][13][14][15][16][17]. The most frequently used ionic liquids in this field are imidazolium salts with various anion species.…”

“…Most of these early reports are rather fragmentary work. Quite recently, some detailed investigation has been reported for the aggregation behavior of nonionic surfactant, Tween 20 [15], and fluorinated cationic surfactant, FC-4 [16], in bmimBF 4 and bmimPF 6 . Although the publication relating to this research subject has been increasing more and more, further accumulation of data obtained by systematically designed experiments is required for better understanding of the aggregation behavior of surfactants in ionic liquids.…”

Supramolecular Structures in the Presence of Ionic Liquids

“…Relative studies on the aggregation of nonionic surfactants in ILs have been reported (Evans et al, 1982;Evans et al, 1983b;Fletcher & Pandey, 2004;Gao et al, 2009b;Li et al, 2008b;Patrascu et al, 2006;Wu et al, 2008). Masahiro et al (Moniruzzaman et al, 2008) reported the formation of reverse micelles in [C 8 mim][Tf 2 N] comprising sodium bis(2-ethyl-1-hexyl) sulfosuccinate (AOT) as surfactant with 1-hexanol as a cosurfactant.…”