Dichroic ratio and order parameters of some sudan dyes doped in nematic liquid crystalline matrix

Polarized absorption spectra of Sudan black B, Sudan III and Sudan IV dyes dissolved in the nematic liquid crystalline (NLC) mixture (W-1680) have been investigated by measuring the intensity of absorption bands in the visible region of parallel aligned samples. The maximum absorbance, dichroic ratio (R) and order parameter (S-dye) have been determined for different concentration of azo dyes in solute-solvent system. The experimental results indicate that dichroic ratio and order parameter increase with addition of dye contents because of strong molecular interactions between the dye molecules and the anisotropic surrounding liquid crystal matrix. (C) 2015 Elsevier GmbH. All rights reserved.