Thermodynamic behaviour of homonuclear and heteronuclear Lennard-Jones chains with association sites from simulation and theory

Monte Carlo simulation and theoretical results are presented for mixtures of associating and non-associating Lennard-Jones chains. The molecular model accounts explicitly for repulsive, dispersive, chain, and association interactions. A modified statistical associating fluid theory for Lennard-Jones chains is used to compare with the NPT and Gibbs ensemble Monte Carlo simulation results. The equation is extended to describe heteronuclear Lennard-Jones chains, and results are compared with those obtained by Monte Carlo simulations. The influence of several variables, such as chain length, segment size and dispersive energy, polydispersity, etc., on the supercritical properties and the phase equilibria behaviour of these systems is discussed here. The theory seems to predict more accurately the behaviour of long chains rather than of those of intermediate length, due to the approximations made in the radial distribution function of the fluid.