Mixed Micelles Containing Alkylglycosides: Effect of the Chain Length and the Polar Head Group

The mixing behavior of binary mixtures of the pure alkylglycosides: β-decylglucoside (β-C 10 G), β-dodecylglucoside (β-C 12 G), β-decylmaltoside (β-C 10 M), and dodecylmaltoside (C 12 M) in combination with different common surfactants has been studied. First, the effect of the nonionic polar headgroup and chain length of the glycosidic surfactants in the mixed micellization with sodium dodecyl sulfate (SDS) was investigated. Further on, to analyze the effect of the ionic headgroup on the micellization of the glycosidic surfactant, β-C 10 G was mixed with different surfactants: dodecyltrimethylammonium bromide (DTAB), dodecylheptaethylene glycol ether (C 12 E 7 ), and β-C 10 M. All the mixed systems under study adapt reasonably well to the model developed by Rubingh, with negative values for the interaction parameter, β m, indicating a favorable interaction between the mixed surfactants. In the mixtures with SDS and the glycosides, the interactions become stronger when the hydrocarbon chain length of the surfactant is shorter and the hydrophilic headgroup is larger, i.e., when the surfactants become more hydrophilic. The β-C 10 G mixes favorably with the other surfactants, the interaction becoming stronger in the order C 12 E 7, β-C 10 M, SDS, DTAB. The strong interaction in micellization with DTAB is explained by assuming an anionic character in the β-C 10 G molecule, as shown by electroosmosis measurements. Finally, the favorable interaction with β-C 10 M is explained by considering the packing between the headgroups of both nonionic surfactants.