On the molecular structure and aggregative properties of Sudan dyes in the anisotropic host

Dichroic ratio R and order parameter S of solutions containing five Sudan dyes in nematic solvents were investigated by the measuring of the intensity of the absorption bands in the visible region of parallel aligned samples. The effective factors such as molecular shape, self-association of the phenolic dye molecules through hydrogen bonding, solvent nature on the visible absorption of the dyes were investigated. Also, from the observed dichroic ratio, the dependence of the order parameter on the shape, size, polarity and steric effect of the substituent was demonstrated and discussed. The role of the anisotropic solvent and ordinary solvent on the self-association of the guest molecules in solution has been investigated without using polarised light. (C) 2000 Elsevier Science B.V. All rights reserved.