Synergistic Interactions in Mixed W/O Microemulsions of Cationic Gemini and Anionic Surfactants

Abstract

Abstract The synergic effect between cationic Gemini imidazolium surfactant [C12(Bim)2-2Br] and anionic surfactant sodium dodecyl sulfate (SDS) on the physicochemical properties of the W/O microemulsions was studied. The properties include the molar fraction of the alcohol at the interfacial layer (Xa i), the molar fraction of the alcohol in the oil phase (Xa o), and the Gibbs free energy change (−Δ Go → i o) of transferring alcohol from the continuous oil phase to the interfacial layer. The W/O microemulsion systems contain C12(Bim)2-2Br-SDS/butan-1-ol/octane/5 % NaCl solution. The values of Xa i and Xa o obtained from the W/O microemulsions containing the mixed surfactants are smaller than that of the microemulsion systems containing the single surfactant C12(Bim)2-2Br or SDS, while the values of −Δ Go → i o are larger. This showed the existence of synergism between [C12(Bim)2-2Br] and SDS. The effects of alcohols, alkanes and NaCl concentrations on the values of Xa i, Xa o and −Δ Go → i o, in the W/O microemulsions stabilized by C12(Bim)2-2Br and SDS were also investigated and discussed.