Volumetric Studies of the Homologous Series of Alkyl-cyano-biphenyl Liquid Crystals

— Measurements are reported of densities as a function of temperature for the homologous series of alkyl-cyano-biphenyl liquid crystals C„H2„ + 1 . 0 . 0 . C N for n = 5 to 9. Cubic B-splines have been fitted to the experimental results and their derivatives have given the coefficients of thermal expansivity. Transitional volume changes have been determined by extrapolation of the densities of phases each side of a transition, and the nematic to isotropic volume changes show a marked odd-even effect. The densities of the nematic and isotropic phases in equilibrium have been used in conjunction with a van der Waals theory of liquid crystals to provide information on mean field potential parameters, transitional order parameters and molecular length to breadth ratios.