Abstract: The foaming and emulsifying properties of three new twin-tailed zwitterionic Gemini surfactants(C8C8L3Sz, C8C8L4Sz, C10C8L3Sz) were studied by modified Ross-Miles method and watershed-time method, respectively. The effects of the concentration of surfactants, molecular structure, and temperature were investigated. Experimental results show that the three surfactants all have good foaming properties, and their maximum foam heights and half-lives exist stable values under experimental concentration. The results show that the longer the hydrophobic chains, the worse the performance of their foaming and the better foam stability. In addition, temperature increasing can make foaming properties better and foam stability worse. The foam stability can be improved by adding either short-chain alcohols or inorganic salts. The most appropriate dosage of the emulsifiers of C8C8L3Sz, C8C8L4Sz and C10C8L3Sz is 6×10-4, 6×10-4 and 4×10-4 mol/L, respectively. It shows the longer the hydrophobic chains, the better the emulsifying properties, and the effects of spacers on emulsifying properties are little. The emulsifying properties become worse by increasing temperature. When the oil phase has the same carbon number, cycloalkanes achieve the best emulsifying effect more easily than straight chain alkanes, but the stable time of emulsion of the two is almost the same. For alkanes with different carbon number, the longer the carbon chains of alkanes, the worse the stability of the emulsion and the better the emulsifying properties.

Key words: zwitterionic gemini surfactants, foam properties, emulsifying properties