Liquid-liquid equilibria for solutions of polydisperse polymers. Continuous thermodynamics for the close-packed lattice model

A continuous thermodynamic framework is presented for phase-equilibrium calculations for solutions of polydisperse polymers. An expression for the Helmholtz function of mixing is based on a mathematically simplified Freed model developed previously. A binary mixture requires a size parameter c r and an energy parameter e; the former can be temperature dependent, while the latter can depend on temperature and chain length. The functional approach is adopted to define thermodynamic functions and to derive expressions for chemical potentials, spinodals, and critical points