ORIENTATIONAL BEHAVIOR OF STILBENE DYES IN NEMATIC LIQUID-CRYSTALS

Four different guest-host systems containing stilbene molecules solved in the liquid crystalline compound CB5 were investigated to study the orientational behavior of these dyes in the nematic phase. The estima tion of the optical order parameter S(op) was done using UV/Vis dichro ism 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 an d the change of the clearing point with the amount of solved dye molec ules. Besides the common decrease of the optical order parameter with increasing dye concentration the opposite behavior, i.e., a slight inc rease of S(op) was observed also.