Membrane equilibria in concentrated polymer solutions

Membrane equilibria in concentrated polymer solutions are investigated. A three-component system (solvent, a polymer and an arbitrary solute) is considered. Starting with the virial expansion of the osmotic pressure, the Gibbs-Duhem equation for the system is integrated and the chemical potentials of the different components are evaluated. From the latter the equilibrium conditions are derived for a variety of experimental situations. The treatment is extended to the study of partition equilibria in gels, using a concentrated polymer solution as a model for the gel.