INCORPORATION OF N-ALKANOLS IN REVERSE MICELLES IN THE AOT N-HEPTANE WATER-SYSTEM

Partitioning of alkanols (from ethanol to n-decanol) between the bulk (n-heptane) solvent and the micellar pseudophase is obtained from their effect upon the fluorescence intensity of indoleacetate anions incorporated into AOT reverse micelles and partially quenched by carbon tetrachloride as a function of the surfactant concentration (at fixed water/surfactant ratios). For all the alkanols considered, the extent of incorporation into the micelles decreases when the water/AOT ratio increases from 4 to 20. At a given water/AOT ratio, the incorporation of the n-alkanol increases when the length of the alkyl chain increases. However, this dependence is small, the partition constant changing by less than a factor of 6 between ethanol and n-decanol. These results are interpreted in terms of an interfacial localization of the polar head of the alkanols in the micellar interface, with the alkyl chains extended toward the bulk solvent.