Aggregation behaviour and solubilization capability of mixed micellar systems formed by a gemini lipoamino acid and a non-ionic surfactant

Abstract

In this work we carried out the physicochemical characterization of mixtures of a non-ionic surfactant and a gemini lipoamino acid one. The mixed systems were studied by surface tension measurements, fluorescence quenching and SAXS determinations. Both surfactants formed mixed micelles in different relationships and the properties of the mixtures were more similar to those of their major component. SAXS analysis showed that the micelles were triaxial ellipsoids, type core shell. The mixtures exhibited non-ideal behaviour, as indicated by critical micelle concentrations (CMC) lower than those of the individual surfactants, and negative interaction parameters, β. The mixed surfactant systems produced enhanced water solubilization of polycyclic aromatic hydrocarbons, viz, naphthalene, phenanthrene and pyrene, quantified in terms of the molar solubilization ratio and the micelle-water partition coefficient. Synergism due to the presence of both surfactants in the mixture was observed for the solubilization of naphthalene and phenanthrene, but not for pyrene. This difference in behaviour might be related to the CMC and structure of the surfactants, the polarity of the solutes, and their association constants with the micellar phase.