Abstract: Surface tensions of sodium N,N′-bis(lauricethylenediamine) di-propionate (DLMC),DLMC/DTAB blend system and DLMC/AEO₆ blend system were determined.The surface chemical parameters of DLMC as well as the blend systems were calculated.Interaction parameters between the two kinds surfactant in surface phase as well as micelle phase of the blend surfactant systems was calculated based upon normal solution theory.Results showed that in NaBr solution with concentration of 0.1 mol·L^-1 under 25 ℃,cmc of DLMC is 1.01×10^-4 mol·L^-1,and γ_cmc is 30.3 mN·m^-1.The γ_cmc,cmc and A_min of DLMC/DTAB blend system all are smaller than that of the single surfactant component in the blend system.The γ_cmc,cmc and A_min of DLMC/AEO₆ blend system decrease at first,and then increase with the further addition of DLMC.The two blend systems exhibit synergic effect in both surface tension reduction capacity and efficiency,as well as capacity for formation of mixed micelles.

Key words: gemini surfactant, sodium N,N′-bis(lauricethylenediamine) di-propionate, surface tension, critical micelle concentration