Investigation of Mixed Micellar Systems of Ionic+C12En Surfactants

Abstract

The micellization process of binary mixtures formed by polyoxyethylene monododecyl ether (C12En; n=12 and 15) and different ionic surfactants, anionic sodium dodecyl sulfate (SDS) and cationic hexadecylpyridinium bromide (CPB), was examined by using surface tension and viscosity measurements. Rubingh's nonideal solution theory predicted nonideal mixing and attractive interaction between the constituent surfactants in the mixed micelle. In the single systems, the relative viscosity of nonionic surfactant is greater than that of the ionic surfactant and increases with the increasing level of ethylene oxide. In the mixed surfactant systems, the relative viscosities vary at a mixed molar fraction between 0.2 and 0.3, and then the relative viscosities of mixed systems decrease with the increasing mole fraction of ionic surfactants. The experimental viscosity values show a positive deviation from ideal behavior because of mixed micelle formation and the electroviscous effect. This effect could be suppressed by the addition of NaCl.