Photophysical characterization of mixed micelles of n-butanol/SDS and n-hexanol/SDS. A study at low alcohol concentrations

The effect of the addition of n-butanol (BuOH) and n-hexanol (HexOH) on the micellization of sodium dodecylsulfate (SDS) has been investigated using fluorescence quenching methods. the binding constants were calculated using an expression which relates the total concentration of alcohols and the micelle concentration. the values of K were 4.67 and 17.6 M-1 for BuOH/SDS and HexOH/SDS, similar to values obtained by other methods. the cmc of SDS decreases on addition of alcohols and goes through a minimum for the BuOH/SDS system. Micellar aggregation numbers (N) were determined from linear plots of Ln (I-0/I) against [Quencher] at low alcohol concentrations. for 15 mM SDS, in the presence of BuOH the N values decrease on addition of alcohol up to 0.2 hi. for HexOH, N can be assumed to be constant up to 4.8 mM, after which N decreases. the polarity of the micellar core containing alcohol was evaluated from the I-1/I-3 ratio of monomeric pyrene. the effect of addition of the alcohol causes a decrease in the I-1/I-3, which corresponds to a decrease in the polarity of the pyrene solubilization site.UNIV FED ESPIRITO SANTO,DEPT QUIM,CCE,BR-29060900 VITORIA,ES,BRAZILWeb of Scienc