Diffusive Transport in Swollen Polymer Membranes

Abstract

Recent work on transport of solvent and solutes in swollen, hydrocarbon-type network polymers is reviewed, and some generalizations for other systems are made. Network polymers are useful as model membranes since they are well understood thermodynamically and can be free of inhomogeneities such as pores and crystallinity which obscure results in many systems. The absence of pores assures a diffusional transport mechanism. The degree of swelling of the membrane by solvent is a very important parameter which for hydrocarbon networks can be varied over a wide range without altering polymer structure by selecting from a large number of suitable organic solvents. Solvent transport by an applied pressure differential as in reverse osmosis is considered as well as by downstream vacuum as in pervaporation. Emphasis is given to how the outside driving force causes solvent diffusion in the membrane and relationships between the two different processes. The major factors affecting the diffusion coefficient of solutes in such membranes are discussed.