Micellization of sodium laurylethoxysulfate (SLES) and short chain imidazolium ionic liquids in aqueous solution

Francesc Comelles; Isabel Ribosa; Juan José González; M Teresa Garcia

doi:10.1016/j.jcis.2014.03.021

Micellization of sodium laurylethoxysulfate (SLES) and short chain imidazolium ionic liquids in aqueous solution

J Colloid Interface Sci. 2014 Jul 1:425:44-51. doi: 10.1016/j.jcis.2014.03.021. Epub 2014 Mar 17.

Authors

Francesc Comelles¹, Isabel Ribosa², Juan José González², M Teresa Garcia²

Affiliations

¹ Department of Chemical and Surfactants Technology, Institute of Advanced Chemistry of Catalonia (IQAC-CSIC), Barcelona, Spain. Electronic address: fcffte@cid.csic.es.
² Department of Chemical and Surfactants Technology, Institute of Advanced Chemistry of Catalonia (IQAC-CSIC), Barcelona, Spain.

PMID: 24776662
DOI: 10.1016/j.jcis.2014.03.021

Abstract

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.

Keywords: Anionic surfactant; Critical aggregation concentration (cac); Critical micelle concentration (cmc); Interaction parameters; Ionic liquids; Mixed aggregates Regular Solution Theory; SLES; Surface tension.