Electric linear dichroism study of some Sudan dyes using electro-optic and spectroscopic methods

Contrast ratios CR and order parameters S of Sudan black B and solutions containing two phenolic Sudan dyes (Sudan III and Sudan IV) in nematic solvents (E7 and E8) were investigated using polarized spectroscopy in a guest-host system based on homogeneous-homeotropic alignment. The orientation of the dye molecules was controlled using an electric field, and this enabled the contrast ratio of the dye to be obtained by electrically switching. The transient molecular reorientation and linear electric dichroism of the guest-host system (Sudan black B-E8) was also investigated in an electro-optical system using the rectangular-shaped pulsed electric field. Moreover, temperature dependence of the order parameter of Sudan black B in the nematic host was studied. (C) 2003 Elsevier B.V. All rights reserved.