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Phase equilibria in polymer solutions



A new semiempirical equation is presented for the Gibbs energy of mixing for solutions of polymers in single and mixed solvents. The equation contains two adjustable parameters per binary mixture and can readily be extended to multicomponent systems without additional parameters. The new expression gives a very good representation of the properties of a variety of polymer solutions including those in which there are strong specific interactions such as hydrogen bonding. Parameters are determined from binary vapor pressure data.

A graphical method based on the new equation is given for predicting solubility limits in ternary systems containing one polymer and a mixed solvent. Only binary data are used. The method is demonstrated by comparisons of predicted solubility behavior with new experimental data taken on systems composed of polystyrene and the following mixed solvents: acetone-toluene, acetone-benzene, methanol-benzene, methanol-ethyl acetate, and acetone-methylcyclo-hexane.

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