Abstract
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, σ, degree of counterion dissociation, αmic, 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, Nagg, 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 αmic and increase of Nagg 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 Nagg, and larger σ. These differences are explained on the basis of the attractive interactions between the voluminous sugar headgroups.
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