ORIENTATIONAL ORDER OF 1,3-DICHLORO-2-ETHENYLBENZENE IN LIQUID-CRYSTAL SOLVENTS

The order parameter matrices of a molecule that has no symmetry, 1,3-d ichloro-2-ethenylbenzene, dissolved in two different nematic liquid-cr ystal solvents are analyzed in terms of various models for the intermo lecular mean-field potential. In a mixture of liquid crystals for whic h the interaction between the molecular quadrupole moment tensor and t he average electric field gradient of the nematic solvent has been min imized, the orientational order is best described by models for the sh ort-range anisotropic potential. The most successful potentials are wr itten in terms of anisotropic interactions between the solute surface and the liquid-crystal mean field. This represents a strong test of su ch models because they simultaneously fit the five independent orienta tional parameters obtained from the same solute, thus removing the pro blems associated with comparing results among different solutes in eit her the same or a different sample tube.