Equations of State and Virial Coefficients for Rigid Linear Chains

Abstract

The study of isotropic−nematic phase transition in a system of rodlike molecules requires an accurate equation of state for the isotropic phase. In this paper, generalized Flory-dimer (GF-D) theory is extended to fluids composed of rigid linear chains, and its predictions of the compressibility factor and virial coefficients are compared with simulation results available in the literature. A simplified equation of state is derived which eliminates the need to evaluate exclusion volumes. Compressibility factor predictions for linear tangent hard-sphere (LTHS) trimers, linear fused hard-sphere (LFHS) trimers, LTHS tetramers, and planar T- and Y-shaped tangent hard-sphere tetramers are in excellent agreement with simulation results. For LFHS 6-mers and 8-mers, with the ratio of bond length l to hard-sphere diameter d of 0.5, GF-D predictions are in good agreement with simulation results only for volume fractions less than about 0.4. At higher densities, GF-D theory first underpredicts and then slightly overp...