Dichroic ratios R and order parameters S of solutions of methylene blue, rhodamine 6G and rhodamine B in the nematic liquid crystalline solvent were investigated by the measuring of the intensity of the absorption bands in the visible region of parallel aligned samples. The molecular association of the dyes in a nematic solvent and also in an amphiphilic solution was studied using optical spectroscopy and in a guest–host system. The nature of the interacting pairs in these dyes was discussed using the exciton theory.
