Statistical associating fluid theory for chains of attractive hard-spheres: Optimized equations of state

Abstract

New equations of state for chain molecules are proposed. The equations of state are physically sound and have a simple mathematical structure. The equations combine the recently developed simplified hard-sphere equations with the first order thermodynamic perturbation theory for chain molecules. The resulting equations of state show almost identical thermodynamic properties compared to the original equation of state for chains of attractive hard spheres. The advantage of the equations proposed here is the simple mathematical structure. They can be written as fourth order or cubic polynomial in the molar volume for which the molar volume can be calculated analytically for given temperature and pressure. This work shows that physically based model equations of state and simple equation structures can be incorporated. Furthermore the equations presented here enlarge the applicability of the statistical associating fluid theory for chain molecules.