Abstract: The interactions of a series of novel cleavable esterquat Gemini surfactants, Cm-1H2m-1COOCH2CH2(CH3)2N+(CH2)n+N(CH3)2CH2CH2OOCCm-1H2m-1]•2Br-(symbolized II-m-n, m=10, 12; n=3, 4, 6), with sodium dodecyl sulphate (SDS) in aqueous solution have been investigated. The experimental results suggested that both II-10-n and II-12-n had evident synergism with SDS in mixed micelle formation and surface tension reduction in binary system. II-10-n manifested stronger synergistic interaction with SDS than II-12-n, which was attributed to the equal-chain length effect. The synergism in mixed micelle formation of II-m-n/SDS was found to become more intense increasingly with the increase of n. The equilibrium constant proof illustrated that the ratio of II-m-n to SDS existed in mixed micelles was approximately 1:1, which indicated that the mixed micelle was charged. Therefore the addition of NaBr could improve the surface activity of II-m-n/SDS mixtures and promote the formation of mixed micelles.

Key words: Esterquat Gemini surfactant, Sodium dodecyl sulphate, Mixed system, Mixed micelle