Calorimetric and NMR Investigations of the Micellar Properties of Sodium Dodecyl Sulfate in Aqueous Mixtures of Isomeric Butanediols

Abstract

The enthalpies (ΔmicH°), entropies (ΔmicS°), and Gibbs energies (ΔmicG°) of micelle formation have been determined for a series of sodium dodecyl sulfate (SDS)/butanediol isomer micelles using isoperibol solution calorimetry. Nuclear magnetic resonance (NMR) paramagnetic relaxation enhancement experiments were used to determine the degree of solubilization of the isomeric butanediols (BTDs) in a 0.100 M solution of SDS micelles. In addition, the manner in which the butanediol cosolvents interact with SDS micelles, as a function of the position of substitution of the hydroxyl groups on the four-carbon backbone, has been examined closely via 13C NMR spectroscopy. All of these results are interpreted in terms of the differences in the interaction of the isomeric butanediols with SDS micelles because of the addition of the second hydroxyl headgroup on the four-carbon backbone of the alcohol, when compared to the well-studied SDS/1-butanol (C4OH) mixed micellar system.