Often membranes for gas separations and other separations are produced by a unique solution processing operation in which a solution of the polymer in a solvent is spun or injected into a non-solvent. During the resulting process, the solvent will diffuse out of the polymer solution and the non-solvent will diffuse in. Consequently, phase separation will occur in which one has a polymer rich phase that contains the solvent, and a polymer poor phase associated with the non-solvent.

The non-solvent phase, after further processing, emerges as pores in the resulting polymer membrane. A fundamental description of this membrane formation process involves detailed information concerning the phase equilibria and the thermodynamics of this three-component polymer-solvent-non-solvent system as well as the diffusion characteristics of the solvent and the non-solvent. The Center has measured and correlated the appropriate thermodynamic behavior for these ternary systems as well as collected measurements concerning diffusion characteristics. These basic thermodynamic and mass transfer properties are critical in accurate modeling of membrane separation processes.