Topological changes accompanying the phase transitions in AOT-water binary system in the presence of a strongly binding counter-ion

Abstract

Self-assembly of amphiphiles in aqueous solution gives rise to diverse liquid crystalline phases with different structures and properties. These phases possess different symmetries and the transition between them is associated with strong topological changes. For example, it is intriguing how the 2-dimensional bilayer sheets transform into 1-dimensional rods (building blocks of hexagonal phase) via a complicated unit involving a node connecting three rods at a certain angle—the type-I Ia3d cubic phase. Using AOT–p-toluidine hydrochloride (PTHC)–water ternary system, we have gained insight into the transformation of the aforementioned building blocks of the different liquid crystalline phases from one symmetry to another during a phase transition. Small-angle X-ray diffractograms indicate that in addition to the Bragg peaks, diffuse scattering dominates the diffraction patterns both in the lamellar as well as the cubic phases present in the ternary system. The diffused scattering was attributed to the increase in the fluctuation which in turn is related to the change in topology associated with the phase transition from the inverse hexagonal to cubic to lamellar phases.