Molecular shape and volume effects on the orientational ordering of simple liquid crystals

Abstract

The parameters characterizing the isotropic–nematic phase transition in liquid crystals have been calculated using a generalized van der Waals theory. The molecules are assumed to have spherocylindrical hard cores, which are treated by scaled particle theory, and to have attractions which go as −C_iso/r⁶_ij −C_ancos²ϑ_ij/r⁶_ij, where ϑ_ij is the angle between the long axes of molecules i and j and r_ij is the distance between their centers. The dependence of phase transition properties on the molecular volume, polarizability, and length‐to‐width ratio are examined; and the importance of the coupling between hard core repulsions and isotropic dispersional attractions is discussed.