Partition Equilibria for Alcohols in Reverse Micellar AOT-Oil-Water Systems Studied by PGSE-FT NMR. A Comparison Between AOT-containing and the Corresponding AOT-free Systems

Microemulsions of the reverse micellar type were investigated by determining the self-diffusion coefficients of the components using the Pulsed Field Gradient Spin Echo – Fourier Transform NMR method (PGSE-FT NMR). The microemulsions were composed of the surfactant AOT, water and an oil (either benzene or cyclohexane), forming a water core in an oil continuum. The primary alcohols ranging from methanol to 1-decanol were added to the microemulsions as a fourth component. The degree of binding, p, of the alcohol to the micelles was determined from the measured self-diffusion coefficients for this component. Partition equilibrium constants were calculated from the values of p. Thermodynamic partition equilibrium constants, K _c , calculated from the partition coefficients are presented and compared with values based on literature data for AOT-free systems. Similarities and differences between these cases are revealed and interpreted.