VAPOR-LIQUID-EQUILIBRIA FOR SOLVENT-POLYMER SYSTEMS FROM A PERTURBED HARD-SPHERE-CHAIN EQUATION OF STATE

Vapor-liquid equilibria (VLE) for solvent-polymer mixtures at modest p ressures are obtained from a perturbed hard-sphere-chain equation of s tate. This equation of state is the sum of a hard-sphere-chain term as the reference system and a van der Waals attractive term as the pertu rbation. The reference equation follows from the Percus-Yevick integra l theory coupled with chain connectivity as described by Chiew. The ef fect of specific interactions, such as hydrogen bonding, is introduced through the proposal of Veytsman based on the statistical distributio n of hydrogen bonds between donor and acceptor sites suggested by mole cular structure. Calculated and observed vapor-liquid equilibria are p resented for nonpolar, polar, and hydrogen-bonding solvent + homopolym er systems. Pure-component parameters (number of segments per molecule , segment-segment energy, and segment diameter) are obtained from pure -component properties: liquid density and vapor pressure data for norm al fluids and pressure-volume-temperature data for polymers. A binary energy interaction parameter must be obtained from limited VLE data fo r each binary system; this parameter appears to be independent of temp erature and composition over a useful range. Theoretical correlations and predictions are in good agreement with experiment.