From reverse worms to reverse vesicles formed by mixed zwitterionic and non-ionic surfactants in cyclohexane

Abstract

The reverse aggregates formed by mixed zwitterionic surfactant, N-dodecyl-N,N-dimethyl-3-ammonio-1-propanesulphonate (abbreviated to SB-12), and non-ionic surfactant, tetraoxyethylene lauryl ether (C₁₂E₄), in cyclohexane have been studied using rheological and small angle X-ray scattering (SAXS) measurements and polarised-microscopy (POM) observations. With the help of C₁₂E₄ and a trace amount of water, SB-12 was dissolved in cyclohexane to obtain a homogeneous solution. The morphologies of the aggregates depended on the molar ratio of C₁₂E₄ to SB-12, β. At β = 1, reverse wormlike micelles were formed, and at β = 2, there were reverse vesicles in the solution. The mechanism underpinning the reverse aggregate formation was discussed. The amount of trace water, represented as the mole ratio of water to total surfactants W₀, did not influence the aggregate morphologies.