Modeling of solution thermodynamics: A method for tuning the properties of blend polymeric membranes

Thermodynamics of polymer blends are modeled and ternary phase diagrams are plotted for various blend compositions using Flory-Huggins theory for polymer solutions. Equations of spinodal curve and plait point for the quaternary systems are derived based on solution thermodynamics. Binodal curves are calculated by minimizing Gibb's free energy for blend system, poly(acrylonitrile) and poly(urethane). Effects of polymer molecular weight and interaction parameters on the phase diagram are quantified. The published data of membrane transport characteristics are correlated with the modeled phase diagram and validated using FESEM and pore-diameter analysis. The reason for increase in the permeability of blend membranes is established with structural changes with the possible formation of hydrogen bond and justified by the infrared spectra analysis of the blend membranes.