Binary mixtures of β-dodecylmaltoside (β-C12G2) with cationic and non-ionic surfactants:: micelle and surface compositions

Surfactants used for practical applications are usually surfactant mixtures because they often exhibit a performance that is superior to the individual surfactants. In the present study binary mixtures of the sugar based surfactant n-dodecyl-beta-D-maltoside (beta-C(12)G(2)) with the cationic surfactant dodecyl trimethylammonium bromide (C(12)TAB) and the non-ionic hexaethylene-glycol dodecyl ether (C12E6), respectively, were investigated at different bulk mole fractions. Surface tension measurements were used to determine the critical micelle concentration and the surfactant composition at the surface. In addition, the regular solution theory was used to calculate interaction parameters as well as the mole fractions of the individual surfactants in the mixed air-water monolayer and in the mixed micelles, respectively. It was found that n-dodecyl-beta-D-maltoside interacts weakly with the cationic surfactant (C(12)TAB) and that it dominates in both the mixed monolayer and the mixed micelles. On the other hand, beta-C(12)G(2) and C12E6 mix ideally in solution. For both surfactant mixtures the surfactant composition at the surface determined by surface tension measurements and by the regular solution theory, respectively, were compared and discussed in detail.