Equations of state for hard chain molecules

Equations of state for hard sphere chain molecules are derived within the framework of second order perturbation theory of polymerization (TPT2). The present formulation differs from the original Wertheim’s treatment by dealing with molecules with a fixed number of beads. However, the two versions yield very close numerical results for chains composed of freely jointed spheres, showing the insensitivity of the pressure of these fluids to polydispersity. The case of star‐like molecules and chain mixtures is also considered. Theoretical predictions are compared to available simulation data, using recent results for the triplet correlation function for hard spheres in rolling contact. Some predictions for the pressure of freely rotating chains and that of trimers as a function of the bond angle are given.