Mixed micelles of triton X100: interaction, composition, stability and micro-environmental properties of the aggregates

Micellization of aqueous binary mixtures of triton X100 (TX100) in the pres ence of sodium dodecyl sulphate (SDS), cetyltrimethylammonium bromide (CTAB ), and octaoxyethylene monodecyl ether (C12E8) has been investigated by the fluorescence probe technique. The critical micelle concentration values of the three binary combinations (TX100-SDS, TX100-CTAB and TX100-C12E8) in t he whole range of compositions, obtained by using the pyrene 1:3 ratio meth od, were analysed in the light of the conventional regular solution theory for mixed micelles, as well as according to the formulation recently propos ed by Maeda (1995, J. Colloid Interface Sci., 172, 98). This last theoretic al approach was found to be very appropriate for describing the nature of t he interactions involved in the formation and stability of the mixed micell es of TX100. Studies on the micropolarity of the mixed aggregates, as sense d by the probe pyrene. indicated that the incorporation of cosurfactant in the TX100 micelle induces the formation of mixed micelles with a more dehyd rated structure. Data obtained from the polarized fluorescence measurements of diphenylbutadiene solubilized in the micellar phase, which were analyse d according to the 'wobling-in-cone' model, showed the appearance of a less ordered micro-environment around the probe as cosurfactant proportion in t he mixed micelle increased. The results obtained indicate that SDS is the c osurfactant which exerts a more pronounced effect on the micro-environment properties of mixed micelles.