This brief describes the development of a new model for realistically characterizing solution-diffusion transport mechanisms in polymeric membranes that are used for separation and purification of organic solvents. Polymeric membranes used in these environments, if not selected appropriately, undergo excessive swelling and compaction resulting in lowered performance or membrane destruction in the long-term. This brief describes the relationship between key parameters from a chemical, mechanical and thermodynamic perspective. Moreover, the authors show how this new model points membrane...