Abstract: Hexadecyl dimethyl tertiary amine and octadecyl dimethyl tertiary amine were separately used as starting material and to be reacted successively with hydrochloric acid and epichlorohydrin to prepare two intermediates,N-(3-chloro-2-hydroxy)propyl-N,N-dimethyl hexadecyl ammonium chloride and N-(3-chloro-2-hydroxy)propyl-N,N-dimethyl octadecyl ammonium chloride.Then ethylene di-amine reacted with the two intermediates successively in presence of sodium carbonate to obtain the product asymmetric Gemini surfactant (symbolized as 16-X-18).The intermediates and the product were characterized by IR and ¹H NMR as well as the surface activities of 16-X-18 were measured by conductivity method.Results showed that Krafft point of the product is below 0 ℃,and its cmc at 25 ℃ is 2.935×10^-5 mol/L.The degree of combination with the counter-ion decreases as the temperature rises.

Key words: Gemini surfactant, asymmetry, bis-quaternary ammonium salt, surface activity