SOLUBILIZATION OF A 3H-INDOLE MOLECULAR PROBE IN SURFACTANT MICELLES AND VESICLES - A SPECTRAL AND PHOTOPHYSICAL STUDY

An absorption and fluorescence spectral study on the solubilization be havior of amino)phenyl]-3,3-dimethyl-5-carboethoxy-3H-indole (I) in so diumdodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB) aqueo us micelles and dioctadecyldimethylammonium bromide (DODAB) surfactant vesicles has been carried out. Using spectral correlations with the p olarity parameters, polarity values corresponding to a dielectric cons tant D of 48, 33 and 36 have been estimated for SDS, CTAB and DODAB re spectively at 298 K. The nature of the binding site has been discussed . In DODAB vesicles, the probe moves in average toward the center of t he bilayer as a function of temperature. This behavior of molecule I i n DODAB has been effectively used to discuss its permeability to exter nal solubilizates. Fluorescence decay time analysis has been used to d iscuss the molecular recognition in these surfactant assemblies. pH ef fects on the ring nitrogen protonation (neutral-monocation equilibrium ) have been carried out and the extent of monocation formation has bee n discussed on the basis of the charge nature of surfactant organized assemblies.