Résumé
The objective of this work was to shed light on the mechanism of micellar solubilisation of model low-molecular-weight solutes exhibiting a limited solubility in water: phenol, butanol, heptanol, and heptanoic acid. Intermolecular forces operating between these molecules and micelles of cetyltrimethylammonium bromide (CTAB) in the vicinity of the CMC were studied using 1H NMR, titration microcalorimetry, specific conductivity, and UV spectroscopy. The solubilisation locus and orientation of the solutes in cationic micelles were inferred from these data. The detailed solubilisation mechanism was dependent on the composition of the system studied and had a competitive character. At low solute concentrations, phenol was located preferentially in the polar mantle and palisade region. In the presence of NaBr and heptanol, phenol molecules were prevented from penetrating deeply into the micelle. When adding butanol or heptanoic acid, phenol was forced to enter the hydrophobic core.