Molecular Orientation of Perylene-Like Dyes in Liquid Crystal 80CB

The polarized absorption and fluorescence spectra of some dichroic fluorescent dyes (derivatives of 3,4,9-perylenetricarboxylic acid and 3,4,9,10-perylenetetracarboxylic acid) oriented in liquid crystal 80CB have been recorded as a function of temperature. On the basis of these spectra the order parameters and and orientational distribution function have been determined. The conclusions about the influence of the molecular structure of the dyes on their orienting properties in uniaxial liquid crystalline phases have been drawn.