PREDICTION OF POLYMER-SOLVENT PHASE-EQUILIBRIA BY A MODIFIED GROUP-CONTRIBUTION EOS

A new group-contribution lattice-fluid equation of stare (CCLF-EOS), w hich is capable of predicting the equilibrium properties of polymer-so lvent solutions was developed by modifying the original GCLF-EOS of Hi gh and Danner. The GCLF-EOS is a group-contribution form of the Panayi otou-Vera equation of state based on the lattice-hole theory. Group co ntributions for the intel action energy and reference volume were deve loped based only on the saturated vapor pressures and liquid densities of low molecular weight compounds. For a mixture, a binary interactio n parameter was introduced into the mixing rules. croup contributions for the binary interaction parameter were developed from the binary va por-liquid equilibria of low molecular weight compounds. This modified GCLF-EOS model gives excellent predictions of solvent activity coeffi cients both at infinite dilution and at finite concentrations. It is s ignificantly better than the original GCLF-EOS model in its prediction capability. The only input required for the model is the structure of the molecules in terms of their functional groups. No other pure comp onent or mixture propel ties of the polymer or solvent are needed.