FLUORESCENCE PROBING INVESTIGATION OF THE SELF-ASSOCIATION OF ALCOHOLS IN AQUEOUS-SOLUTION

The fluorescence emission spectrum and the lifetime of pyrene solubilized in short-chain alcohol-water mixtures have been determined as a function of composition in the whole composition range and of temperature between 10 and 40-degrees-C. The polarity index I1/I3 (ratio of the intensities of the first and third vibronic peaks in the pyrene emission spectrum) and the lifetime show rapid variations at above an alcohol mole fraction which decreases when the alcohol hydrophobicity is increased. These variations have been attributed to the alcohol self-association. The resulting alcohol aggregates appear to be short-lived and to have some of the properties of micelles of conventional amphiphiles.