Polymeric membranes suffer from plasticization in gas separation, extensive swollen in pervaporation, nanofiltration, and fuel cells by losing performance. Growing research has experimentally realized that the membrane performance could be stabilized by blending with inert second polymer or imbedding in a porous inert confinement. In this article, we introduce a generic model based on Flory-Rehner's swelling theory to describe various membrane processes using a measurable parameter. We assume the membrane polymer to be a network and the constraint as an expandable structure with an energy density equal to its E-Modulus. The model reveals that the isotropic constraint is far more efficient in swelling control. (C) 2008 Wiley Periodicals, Inc.