Abstract: The critical reverse micelle concentrations of quaternary ammonium Gemini surfactants C12-s-C12•2Br (s=2, 3, 4, 5, 6, 8, 12) in n-heptane (cmcw) have been determined by water solubilization method. These values are smaller than the critical micelle concentration (cmcaq) of them in aqueous solution, where C12-s-C12•2Br forms normal micelles. The cmcw as a function of s goes through a maximum at s=4, which is similar to the variation regularity of cmcaq with s. The saturation amounts of water solubilized in the reverse micelles measured by both water solubilization method and conductivity method show a maximum at about s=5. This is attributed to the change of folded conformation of the spacer chain.

Key words: Quaternary ammonium Gemini surfactants, Heptane/hexanol solution, Reverse micelle, Solubilizing water