Surface adsorption and aggregate formation of aqueous binary mixture of cationic surfactant and sugar surfactant

The surface tension of aqueous solutions of dodecyltrimethylammonium bromide (DTAB) and octyl-β-d-glucopyranoside (OG) mixture was measured as a function of the total molality of surfactants and the relative proportion of OG under atmospheric pressure at 298.15 K by drop volume technique. The results of surface tension measurements were analyzed by originally developed thermodynamic equations then phase diagrams of adsorption and micelle formation were constructed. From the analysis of surface tension data, it was suggested that the addition of relatively small amount of DTAB molecules helps the denser monolayer formation compared with the ideal mixing. Furthermore, it was also suggested that the phase diagram of micelle formation has a negative azeotropic point and that the interaction between different components is stronger in the mixed micelle than in the adsorbed film from the view point of the excess Gibbs energy. From these results, it is concluded that the hydrogen bond formation between OG molecules is the main contribution to determine the physical properties in the adsorbed film whereas the ion–dipole interaction between head groups of different components becomes main cause of attractive interaction in the micelle.