A SEGMENT-BASED LOCAL COMPOSITION MODEL FOR THE GIBBS ENERGY OF POLYMER-SOLUTIONS

A segment-based local composition model is presented for the Gibbs energy of polymer solutions. The model represents a synergistic combination of the Flory-Huggins description for the configurational entropy of mixing molecules of different sizes and the Non-Random Two Liquid (NRTL) theory for the local composition contribution from mixing solvents and polymer segments. It reduces to the well-known NRTL equation if polymers are removed from the system. The model provides a most flexible thermodynamic framework to correlate the phase behavior of polymer solutions. The utility of the model was demonstrated with successful representation of vapor-liquid equilibrium and liquid-liquid equilibrium of single solvent, single polymer systems.