Linear dichroism and order parameters of nematics doped with azo dyes

We investigated solvent-solute effects using dye-doped nematic liquid crystals (NLCs) where three Sudan dyes of different concentrations were used as solutes doped into high- and low-polar NLCs as anisotropic solvents. The polarized spectroscopic absorption, dichroic ratio (R), and order parameter (S) were measured, which showed that the rod-like Sudan black B had a higher S and R due to a higher anisotropic solvent-solute effect produced by transition moment and global charge transfer along the molecular axis induced by high polar NLC. The order parameters measured by the Vuks method also showed a higher solvent-solute effect for the high-polar NLC.