Exploratory Study of the Effect of Polar Solvents upon the Partitioning of Solutes in Nonaqueous Reverse Micellar Solutions

JUANA J. SILBER; R. DARÍO FALCONE; N. MARIANO CORREA; M. ALICIA BIASUTTI; ELSA ABUIN; EDUARDO LISSI; PAOLA CAMPODONICO

LANGMUIR

Año: 2003 vol. 19 p. 2067 - 2071

0743-7463

An exploratory study on the effect of polar solvents upon the partitioning of solutes in nonaqueous reverse micellar solutions composed by n-heptane/AOT/polar solvent has been performed. Ethylene glycol (EG), propylene glycol (PG), glycerol (GY), formamide (FA), dimethylformamide (DMF), and dimethylacetamide (DMA) were employed as water substitutes. The study has been carried out at a single value of the mole ratio between the polar solvent and AOT, Ws ) [polar solvent]/[AOT] equal to 2. 9-Anthracenemethanol (9-AM) and acridine orange base (AOB) were the solutes considered. Partitioning of (9-AM) was determined following a fluorescence quenching method. AOB partition constants were evaluated by a method based on the dependence of the absorption spectra with AOT oncentration. The results obtained show that, for both solutes, partitioning to the micelles is strongly favored in (EG), (PG), (GY), or (FA), rather than in (DMF) or (DMA) containing micelles. This trend is opposite to that observed for the partition of the solutes between n-heptane and the bulk polar solvents. The main driven forces to incorporate 9-AM and AOB to the nonaqueous reverse micelles seems to be related with solvent-AOT headgroups and solute-AOT headgroups and counterion interactions.