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

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.