Micellization of sodium laurylethoxysulfate (SLES) and short chain imidazolium ionic liquids in aqueous solution.
In the present study the interactions between an anionic surfactant sodium laurylethoxysulfate (SLES) and three short chain imidazolium (1-butyl-3-methylimidazolium) based ionic liquids (bmim-octyl SO4, bmim-methyl SO4 and bmim-BF4) in aqueous solution have been investigated. Generally when a surfactant is dissolved in a hydrophilic ionic liquid aqueous solution the critical micelle concentration (cmc) obtained is attributed to the surfactant because the ionic liquid (IL) is considered to be only a cosolvent. However, some short hydrophilic ionic liquids posses surface activity in aqueous solution and behave like a surfactant. In that case mixed aggregates between surfactant and ionic liquid can be formed. The three SLES/IL systems here studied have been treated as typical binary surfactant mixtures in aqueous solution. Surface tension measurements have revealed that mixed aggregates and monolayers of surfactant and ionic liquid instead of single surfactant are responsible for the surface active properties of these aqueous solutions. From the Regular Solution Theory, negative interaction parameters (β) for mixed aggregates and monolayers have been found for all SLES/IL mole ratios indicating synergism between the anionic surfactant and the ionic liquids.
Department of Chemical and Surfactants Technology, Institute of Advanced Chemistry of Catalonia (IQAC-CSIC), Barcelona, Spain. Electronic address: fcffte@cid.csic.es.
Francesc
F
Comelles
Department of Chemical and Surfactants Technology, Institute of Advanced Chemistry of Catalonia (IQAC-CSIC), Barcelona, Spain.
Isabel
I
Ribosa
Department of Chemical and Surfactants Technology, Institute of Advanced Chemistry of Catalonia (IQAC-CSIC), Barcelona, Spain.
Juan José
JJ
González
Department of Chemical and Surfactants Technology, Institute of Advanced Chemistry of Catalonia (IQAC-CSIC), Barcelona, Spain.
M Teresa
MT
Garcia
Anionic surfactant; Critical aggregation concentration (cac); Critical micelle concentration (cmc); Interaction parameters; Ionic liquids; Mixed aggregates Regular Solution Theory; SLES; Surface tension