Sugar-based surfactants:: Adsorption and micelle formation of sodium methyl 2-acylamido-2-deoxy-6-O-sulfo-D-glucopyranosides

Aggregation in aqueous solutions of sodium methyl 2-acylamido-2-deoxy-6-O-sulfo-D-glucopyranoside surfactants has been studied, where the acyl group is octanoyl, dodecanoyl, or hexadecanoyl. Critical micelle concentration, cmc, minimum area per surfactant at the air/solution interface, sigma, degree of counterion dissociation, alpha(mic), and thermodynamic parameters (Gibbs free energy, enthalpy, and entropy) of adsorption and/or micellization were calculated from surface tension and conductance measurements. Static and quasi-elastic light scattering measurements were employed to obtain micellar weight-average molecular weight, aggregation number, N-agg, and hydrodynamic radius. Finally, the fluorescence spectrum of solubilized pyrene was employed for determination of micellar polarity. The similarities between these aminoglucose-based surfactants and simple anionic ones include decrease of cmc and of alpha(mic) and increase of N-agg as a function of increasing the chain length of the hydrophobic group. Compared to simple anionic surfactants, the sugar-based counterparts showed more favorable free energies of adsorption and micellization, higher N-agg, and larger sigma. These differences are explained on the basis of the attractive interactions between the voluminous sugar headgroups.