THERMODYNAMIC STUDY IN AQUEOUS MICELLAR SOLUTIONS AT 298.15 K - COMPARISON OF THE INTERACTIONS BETWEEN IONIC SURFACTANTS (SDS AND CTAB) AND1-ALCOHOLS OR PHENOL

Densities and heat capacities of the ternary systems water + surfactan ts (SDS or CTAB) + alcohols (C-4-C-6) or phenol have been measured in the aqueous domain at 298.15 K. Transfer molar volumes and transfer mo lar heat capacities of alcohols or phenol from water to water + SDS or water + CTAB were deduced therefrom. In both surfactants, the variati ons of the transfer quantities of alcohols are typical of the partitio n of an amphiphilic solute between aqueous and micellar phases, depend ing on its hydrophobicity, and moreover, they reveal postmicellar tran sitions. In contrast, phenol behaves differently. In SDS solutions, th e variations of transfer properties are similar to what is observed wi th alcohols, but in CTAB solutions, particularly large variations are observed for a phenol/CTAB ratio of between 1 and 2. At the same time, the viscosity of these solutions increases, and viscoelasticity appea rs. The formation of a strong complex between the positive quaternary ammonium polar heads of the surfactant and phenol resulting from the w eak acidic character of phenol, is certainly responsible for the evolu tion of the transfer properties and for the viscosity of CTAB solution s in the presence of phenol.