A disordered lamellar structure in the isotropic phase of a ternary double-chain surfactant system

et leurs predictions confrontees aux resultats experimentaux. Abstract. 2014 The « anomalous » fluid isotropic phase in the DDAB/tetradecane/water system differs in important ways from microemulsion phases in related systems, and is thus a useful test for models. On the basis of absolute scaled neutron and X-ray scattering data we show here that the microstructure is best characterised as a randomly folded reverse bilayer. All previously reported examples of this structure are restricted to a narrow range of composition and temperature. In this case of a stiff bilayer with low spontaneous interfacial curvature it extends over a large region of the ternary phase diagram at room temperature, the boundaries of which are explained in terms of simple geometric constraints. Other possible microstructures are