Simplified Hole Theory Equation of State for Liquid−Liquid Equilibria of Polymer Solutions and Blends

In our previous work (Wang et al., 1997), the simplified hole theory equation of state was successfully used for the estimation of the pressure−volume−temperature relationship and vapor−liquid equilibria of a large number of polymers, solvents, and their solutions. Here, we extend the equation of state to liquid−liquid equilibria (LLE) calculations for a variety of polymer−solvent and polymer−polymer systems. Analytical expressions for the calculation of the LLE are derived, which make the determination of critical solution point, spinodal, and binodal curves convenient and reliable. Several types of LLE calculations are carried out, including predictions and correlations of spinodals and estimations of binodal and spinodal curves. The results indicate that the equation of state is capable of describing fairly the LLE for polymer−solvent and polymer−polymer systems including the upper and/or lower critical solution temperature phase behavior.