Effect of isopropanol on the micellization of binary mixture containing amino sulfonate amphoteric surfactant in aqueous solution: Mixing with sodium dodecylbenzene sulfonate

Abstract

The effect of isopropanol (IPA) on the micellization behavior of binary surfactant mixtures of an amphoteric sodium 3-(N-dodecyl ethylenediamino)-2-hydropropyl sulfonate (C12AS) with an anionic sodium dodecylbenzene sulfonate (SDBS) was investigated in the water–IPA mixed solvent media (the concentration of IPA in bulk solution varies within the range of 0–100g/L). The values of critical micelle concentration (cmc) of individual surfactants and their mixtures were determined by both the conductometry and the UV–vis spectrometry. Based on the regular solution theory, pseudophase separation model, and some thermodynamic models, the effect of IPA on the micellization parameters and the thermodynamic parameters was theoretically discussed. The addition of IPA in aqueous solution not only changes the polar of solution but also influences the solvation of ionic surfactant, consequently resulting in the change in the mixed cmc values and the molar fraction of components in mixed micelle. The synergistic effect between two surfactants may be decreased with increasing IPA. Thermodynamic data show that the presence of IPA may be not an advantage to the spontaneous process of micellization, and influences the contribution of entropy in the process of micellization. Specially, these cases can be obviously observed at a high concentration of IPA in aqueous solution. These results help us to understand the advantage and the disadvantage of the effect of cosolvent (specially IPA) on the micellization of mixed surfactants and to design the surfactant formulas relative to cosolvent.