Structure in microemulsions of di-chained surfactants

Abstract

Small-angle neutron scattering (SANS) is used to probe structure in water-in-oil microemulsions containing n-alkyl-n-dodecyldi-methylammonium bromides [R₁(C₁₂H₂₅)N(CH₃)₂⁺Br^–], with R₁-n-C₁₀, n-C₁₄, n-C₁₆ and n-C₁₈. The data from a core-shell-drop contrast series at the solubilisation phase boundary are analysed using a model that is sensitive to the surfactant film composition. The results suggest that there is a small amount of cyclohexane penetration into the negatively curved monolayer. For example with the n-C₁₈ surfactant, the volume fraction of C₆D₁₂ in the film is ca. 0.08.