SOLUBILIZATION OF DECANE INTO THE TERNARY-SYSTEM TDMAO 1-HEXANOL/WATER/

We studied the effect of solubilization of a hydrocarbon (decane) into the ternary surfactant system tetradecyldimethylamine oxide (TDMAO)/1 -hexanol/water. For not too high hexanol concentrations, i.e. before i n the ternary system a conventional lamellar phase is formed, it is al ways possible to achieve an one-phase O/W microemulsion. For intermedi ate hexanol concentrations a vesicle phase is formed, which upon solub ilization of decane is transformed into the microemulsion phase. This transition has been monitored by means of electrical conductivity and viscosity, The solubility of decane depends largely on the amount of c osurfactant (1-hexanol) present, and an increase of about a factor of 30 compared to the binary TDMAO system may be achieved. Close to the s olubilization capacity the structure is always of the droplet type whe re the droplet radius increases linearly with the hydrocarbon content, SANS experiments in the shell contrast revealed that these droplets a re fairly monodisperse, and analysis of the results also showed that t he hexanol should mainly be located in the amphiphilic shell that surr ounds the hydrocarbon core. Finally the structural parameters, radius R and polydispersity index p, and the macroscopic interfacial tension were compared to a microemulsion theory that relates these quantities to the elastic properties of the interfacial film. General agreement w ith these predictions has been found, and values for the elastic const ants have been estimated.