EQUATION OF STATE FOR SMALL, LARGE, POLYDISPERSE, AND ASSOCIATING MOLECULES

Statistical Associating Fluid Theory (SAFT) has been extended to many real, molecular, and macromolecular fluids, such as chain, aromatic, and chlorinated hydrocarbons, ethers, alkanols (aliphatic alcohols), carboxylic acids, esters, ketones, amines, and polymers, having molar mass up to 100000. The key result of this work is an accurate and physically sound equation of state for predicting density, vapor pressure, and other fluid properties. Practical calculations require three nonspecific parameters: segment number, segment volume, and segment-segment interaction energy (segment energy for short). For chain molecules, the segment volume and segment energy are found to be nearly constant upon increasing the molar mass, while the segment number is found to be a linear function of molar mass. As a result, this equation of state represents a useful, predictive correlation for many compounds, such as polymers, where no extensive experimental data are available and where parameters have to be estimated based on molar mass and chemical structure only. Specific interactions, such as hydrogen bonding, are characterized by two association parameters, the association energy and volume, characteristic of each site-site pair. These parameters, having well-defined physical meaning, control the bond strength and hence the degree of association. © 1990, American Chemical Society. All rights reserved.