Mixed micellar properties of a cationic gemini surfactant and a nonionic surfactant

The mixed aqueous properties of a geminic surfactant (1,2 bis(dodecyldimethylammonium) ethane dibromide, 2RenQ) and a nonionic surfactant (hexaoxyethylenedodecylether, C12E6) were studied by means of surface tension, fluorescence,H-1 NMR and light scattering. The mixed critical micelle concentrations (CMCs) were intermediate between the respective surfactants' CMCs, and the interaction parameter was obtained as -2.2. The micropolarity determined by pyrene was very similar over a wide range of mixed ratios. The results obtained from NMR and lightscattering measurements show that the polar group of 2RenQ is incorporated near the surface of ethylene oxide chains of C,,E, in the mixed micelles whose aggregation numbers are identical over a wide range of mixed ratios and are significantly smaller than those of the respective micelles. These micellar properties reflect the solubilization of azobenzene: the solubilized amounts in the mixed micelles are quite smaller than those in the respective micelles. (C) 1998 Elsevier Science B.V.