Formation of mixed micelles in an aqueous mixture of a biamphiphilic surface active ionic liquid and an anionic surfactant: Experimental and theoretical study

Abstract

The micellization behaviour of biamphiphilic surface active ionic liquid (BAIL), 3-methyl-1-pentylimidazolium dodecylsulfate [C5mim][C12SO4] with anionic surfactant, sodium dioctylsulfosuccinate (AOT) was investigated using different techniques in an aqueous solution. The values of critical micelle concentration (cmc) and thermodynamic parameters have been ascertained by employing conductometric measurement at (298.15, 308.15 and 318.15) K. The interfacial parameters viz. surface pressure, maximum surface excess concentration, and minimum surface area per surfactant molecule evaluated by using the surface tension measurement at 298.15 K shows the less effectiveness of mixtures to reduce the surface tension. The size and turbidity of the mixed aggregates were investigated using dynamic light scattering (DLS) and turbidimetry. The turbidity results show the existence of micelles as well as mixed aggregates. Different proposed theoretical models like Clint, Rubingh and Motomura was employed for the evaluation of mixed micellar parameters (ideal values of cmc, activity coefficients of the components in the mixed micelle, and interaction parameters etc.) at different compositions. The existence of both the interactions (synergistic and antagonistic) has been inferred in the studied system. The mixed micelle formation was found dependent on micellar composition.