Order in the Nematic Mesophase

The degree of order, θ33 of a paramagnetic probe, vanadyl acetylacetonate, has been measured in the nematic mesophase of eight liquid crystals. Significant deviations from a common curve are observed when θ33 is plotted as a function of the reduced temperature. Calculations using the specific form suggested by Maier and Saupe for the intermolecular potential function, describing both solvent-solvent and solute-solvent interactions, fail to provide a quantitative account of the deviations. The calculations do, however, account qualitatively for the behaviour of different solutes aligned in the same nematic mesophase. The deviations appear to depend, in a systematic way, on the nematic-isotropic transition temperature which suggests that a modification to the intermolecular potential could describe the experimental results.