Orientational Behavior of Stilbene Dyes in Nematic Liquid Crystals

Abstract

Four different guest-host systems containing stilbene molecules solved in the liquid crystalline compound CBS were investigated to study the orientational behavior of these dyes in the nematic phase. The estimation of the optical order parameter, S_op was done using UV/Vis dichroism measurements. The dye's structure and concentration influence the nematic phase order and the phase range. This will be demonstrated in concentration dependent measurements of the optical order parameter and the change of the clearing point with the amount of solved dye molecules. Besides the common decrease of the optical order parameter with increasing dye concentration the opposite behavior, i.e., a slight increase of S_op , was observed also.

Key Words:

• guest-host systems
• stilbene dyes
• optical order parameter
• phase transition temperature