Abstract:
This paper reviews the solution behavior of cetyltrimethylammonium hydroxynaphthalene carboxylate (CTAHNC), which has the unique feature of undergoing a transition from vesicle to worm-like micellar phase in three different ways, namely, increase in temperature, addition of a surfactant and on shearing. Fluorescence anisotropy, NMR, rheology, small angle neutron scattering studies etc gave evidence of the vesicle-micelle transition. CTAHNC can be looked upon as a complex formed by two oppositely charged surfactants (CTA(+) and HNC-). This ion pair effectively acts as a double-chain lipid and has a tendency to form vesicles. On increasing the temperature, and/or adding single chain surfactants or shearing, the complex dissociates which changes the curvature energy of the surface. This leads to a 'surface melting' that brings forth the vesicle-micelle transition.