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Phase behavior and second osmotic virial coe¿cient for competitive polymer solvation in a mixed solvent solution



Jack F. Douglas, Jacek Dudowicz, Karl Freed


The recently developed Flory-Huggins (FH) type general theory for competitive solvation of polymers by two mixed solvents is extended to explain phase boundaries and the variation of the solvent quality, as determined by the second osmotic virial coefficient B2, with temperature and solvent composition. The resulting complexity of the polymer miscibility variation in these ternary mixtures arises from the competitive associations between the polymer and solvents and from the coupling of these interactions to the weak van der Waals interactions between all the mixture components. Our main focus lies in determining the influence of the free energy parameters (governing solvation) and the effective FH inter-action parameters {χαβ } (driving phase separation) on the phase boundaries (specifically spinodals), the second osmotic virial coefficient B2, and the relation between spinodals and B2. Our classification of the possible miscibility patterns is relevant to numerous applications of ternary polymer solutions in industrial formulations and measurements performed for mixed solvent systems for the purpose of polymer characterization, such as chromatographic separation where mixed solvents are commonly employed. A favorable comparison of B2 with experimental data for ternary polymer solutions supports the validity of our theoretical predictions, although the limitations of mean field theory in describing polymer solution properties must be recognized.
Journal of Chemical Physics


polymer, mixed solvents, competitive solvation, virial coefficients, Flory-Huggins theory, co-non-solvency


Douglas, J. , Dudowicz, J. and Freed, K. (2015), Phase behavior and second osmotic virial coe¿cient for competitive polymer solvation in a mixed solvent solution, Journal of Chemical Physics (Accessed July 14, 2024)


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Created November 21, 2015, Updated January 27, 2020