Gemini surfactant behavior of conventional surfactant dodecyltrimethylammonium bromide with anionic azo dye Sunset Yellow in aqueous solutions

Abstract

• DTMABr may exhibit a gemini surfactant behavior in surfactant-dye solutions. • Surfactant/dye interactions have a role in exhibiting this behavior of DTMABr. • H-/J-aggregations of Sunset Yellow depends on its concentration in DTMABr solution. In this study, the interaction of an anionic azo dye Sunset Yellow with conventional cationic surfactant dodecyltrimethylammonium bromide (DTMABr) has been examined as a function of the dye concentration at 25 °C by electrical conductivity and UV–VIS spectroscopy measurements. Carpena’s method, combined with Aguiar’s approach, was applied to the analysis of the conductivity data for evaluating the micellization parameters such as critical micelle concentrations (cmc), degree of counterion bindings (β), and micellization Gibbs free energies (Δ mic G) from the specific conductivity-surfactant concentration curves. The UV–VIS absorption spectroscopy measurements were performed to obtain information on the dye concentration dependence of the stacking properties of Sunset Yellow in water. The results indicated that although DTMABr is a conventional surfactant with a single alkyl chain, it shows gemini surfactant behavior at relatively high dye concentrations as a result of the surfactant-dye interactions. To the best of our knowledge, this is the first study that shows both the gemini surfactant behavior of DTMABr in the presence of SSY and J-aggregations of SSY at high SSY concentrations in the presence of DTMABr. Furthermore, in the presence of DTMABr, the SSY molecules at low concentrations form H-aggregates; they show J-aggregation at high concentrations.