An empirical method to predict the liquid-liquid equilibria of binary polymer systems

An empirical method is described to predict the liquid-liquid equilibria of several binary systems of polymers in both polar and nonpolar solvents according to a simple modification of the Flory-Huggins equation. The method hinges on a two-step procedure: (i) first, the UCST or the LCST points are calculated by using a previous method proposed by the author and based on the knowledge of a few pure-component properties only; (ii) second, starting from these points, all the miscibility gap is calculated by applying a thermodynamic constraint and simple empirical rules. The predicted results are in fair accordance with the experimental data in both the low- and high-temperature ranges. The correlation of the hourglass phase diagrams is also considered.