INTERACTION OF IODINE WITH AEROSOL-OT IN REVERSED MICELLES IN N-HEXANE

The interaction between iodine and AOT in reversed micelle solutions of AOT in n-hexane is reported. The absorption spectrum of iodine exhibits two bands in n-hexane: lambda(max) = 520 and 290 nm. When AOT is added a new absorption band appears at 385 nm. This band shifts hypsochromically and its intensity increases when the surfactant concentration is increased. The intensity of the 290-nm band also increases while that of the 520-nm band decreases. The existence of an isosbestic point at 488 nm may indicate an equilibrium between the iodine and the surfactant. When water is added to AOT-I2 solution in n-hexane the lambda(max) of the band at 380 nm at W = 0 shifts to 360 nm at W = 15, while its intensity dramatically decreases. Also, the band intensity at 290 nm decreases while that at 520 nm increases. The isosbestic point observed without water is maintained. Thus, water seems to decrease the magnitude of the interaction observed on increasing [AOT]. These results are interpreted in terms of the formation of electron donor-acceptor complexes between AOT and 12. A strong 1:1 outer complex that develops in a 1:2 inner complex depending on the relative concentrations of 12 and AOT micelles is proposed. Both complexes seem to be formed at the micelle interface, showing a microenvironment polarity dependency. The changes are much more significant in the micelle domain (at W < 10) than in the microemulsion domain. This interaction has been quantified as a function of W and AOT concentration. (C) 1994 Academic Press, Inc.