Sugar-Based Surfactants:  Adsorption and Micelle Formation of Sodium Methyl 2-Acylamido-2-deoxy-6-<i>O</i>-sulfo-<scp>d</scp>-glucopyranosides

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, α 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 α 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 σ. These differences are explained on the basis of the attractive interactions between the voluminous sugar headgroups.