title: Interfacial tension in phase-separated aqueous cationic/anionic surfactant mixtures.
abstract: Interfacial tensions in two aqueous phase-separated cationic/anionic surfactant mixtures, CTAB/AS and 12-3-12/AS, without and with NaBr added were determined by the spinning drop method at 318.15 K. CTAB, 12-3-12 and AS are the abbreviations for cetyltrimethylammonium bromide, 1,3-propanediyl-bis(dodecyldimethylammonium bromide) and sodium dodecyl sulfonate, respectively. The interfacial tension sigma was found to be in the range of 0.06-21 microNm(-1). Toward a better understanding of the influence of the concentration difference between the separated phases in aqueous two-phase systems (ATPS) to interfacial tension, compositions of equilibrium phases were determined by elemental analysis coupled with material balance and electroneutrality. The investigation indicates that the concentration differences of surfactant ions between the separated phases and the adsorption of surfactant ions at the interface are the decisive factors determining the magnitude of interfacial tension.
authors.affiliation: Department of Chemistry, State Key Laboratory of Chemical Engineering, East China University of Science and Technology, Shanghai 200237, China.
authors.forename: Yan-Qing
authors.initials: YQ
authors.lastname: Nan
authors.forename: Hong-Lai
authors.initials: HL
authors.lastname: Liu
authors.forename: Ying
authors.initials: Y
authors.lastname: Hu