A family of alkyl sulfate gemini surfactants. 1. Characterization of surface properties

The fundamental aqueous and surface properties of a family of sulfate gemini surfactants have been characterized. The critical micelle concentrations (cmc) were determined by both electrical conductivity and surface tension methods. The cmc values were found to be two orders of magnitude lower than those measured for single tail surfactants. The cmc values depend primarily on the surfactant tail length, and relatively little on the spacer length and solution temperature. The surface tension measurements suggest that current family of gemini surfactants have higher tendency to spontaneously adsorb at the air-water interface and thus are much more efficient in reducing surface tension than conventional single-chain surfactants. Thermodynamic calculations of Gibbs free energies for micellization and adsorption indicate surface adsorption is promoted more than micellization for these sulfate gemini surfactants. This type of molecules may therefore be very efficient and cost-effective in applications that require ultra-low interfacial tensions and high interfacial activities.