Studies of non-solvent induced polymer coagulation by magnetic resonance imaging

It is widely accepted that the morphology of a polymer membrane depends strongly on the conditions prevalent during coagulation. In particular, the composition changes which occur prior to coagulation and the subsequent phase change affect morphology and this, in turn, controls porosity, permeability and selectivity. For many applications, the optimal membrane structure combines a thin, dense layer for selectivity at high flux rates with a thicker, highly porous layer for mechanical strength. While there have been many studies into the development of membrane structures, these have largely relied on calculated composition changes using diffusion-based models. Magnetic resonance imaging has shown great benefit in studies of diffusion in polymers. In the present work, it has been used to follow composition and structural changes taking place during the coagulation of cellulose diacetate solution in acetone by immersion in water. (C) 2001 Elsevier Science Ltd. All rights reserved.