Ionic self-assembly of dye-surfactant complexes: Influence of tail lengths and dye architecture on the phase morphology

The structure and phase behavior of a class of multiple negatively charged azo-dyes complexed with a homologous series of cationic surfactants were examined by differential scanning calorimetry, diverse microscopy techniques, and small- and wide-angle X-ray scattering. It turned out that the resulting dye-surfactant complexes do form highly organized supramolecular architectures, which are crystalline/liquid crystalline in nature. The phase structure and the onset of thermal phase transitions depend both on the substitution pattern of the dye scaffold as well as on the sterical demands and volume fractions of the surfactant tails. This class of materials also shows a number of interesting physicochemical properties, namely, liquid crystalline phases with pronounced optical anisotropy.