Micellization of a Zwitterionic Gemini Surfactant and its Interaction with Anionic Surfactant in Aqueous Medium

Abstract

A surface properties of a sulfobetaine–type zwitterionic gemini surfactant with the structure of 1,2-bis [N-methyl-N-(3-sulfopropyl) -dodecylammonium] ethane betaine (ZGS12), were investigated in aqueous solution . The critical micelle concentration (CMC) of the gemini surfactant at different temperatures and mixed micelle properties of ZGS12 and sodium dodecyl benzene sulfonate (SDBS) were investigated. The results show that cmc of the gemini surfactant (ZGS12) decreases with raising temperature, Gibbs free energy changes and entropy changes are negative and postive, respectively, indicating the formation of micelle is spontaneous and driven mainly by entropy. According to the theory of regular solution , interaction parameters between the zwitterionic gemini surfactant ZGS12 and the anionic surfactant SDBS indicate strong attractive interaction and great degree of synergism in micelle formation due to weakening of the electrostatic head group repulsion.