Competition between intermolecular and intramolecular association in flexible hard chain molecules

Abstract

A new theory to explain the competition between inter- and intramolecular association in flexible hard chain molecules is presented. The theory has been tested through comparisons with Metropolis Monte Carlo simulation results. For intermolecular association we use Wertheim’s theory which has been shown to be accurate for intermolecular association in flexible associating hard chain molecules. For intramolecular association we use a theory we developed for intramolecular association in the absence of intermolecular association. These two theories are combined to develop a theory for the competition between inter- and intramolecular association. The new theory is in good agreement with simulation results and is able to predict some salient features of associating chain molecules. The theory predicts that intermolecular association becomes more important at high densities and that intramolecular association dominates at low density and low temperatures. In addition, theory and simulation show a minimum in the compressibility factor when plotted against the association energy at low density. This minimum is due to the presence of intramolecular association and is not observed for intermolecularly associating fluids.