MASS-TRANSPORT THROUGH POLYMERIC MEMBRANES

Mass transport through three polymeric membranes (Cuprophan, poly(acrylonitrile), and a poly(acrylonitrile) membrane with an adsorbed protein layer) is studied. A series of eight compounds ranging in molecular weight from 60 (urea) to 1355 (vitamin B12) were investigated. A complete set of transport properties are reported including the permeability coefficient, sieving coefficient, pressure-filtration coefficient, and frictional coefficients representing the interactions of solute-membrane, solute-solvent, and solvent-membrane. Solute permeability for diffusive transport correlates well for all membranes studied with solute molal volume except for sulfobromophthalein (BSP). Because of strong membrane-solute frictional interactions, BSP has a reduced permeability. The sieving coefficient, which characterizes convective transport, also correlated with solute molal volume except for BSP and the lipophilic compound thiopental. The reduced convective transport of BSP is again due to its high frictional interactions with the membranes. The sieving coefficient for thiopental is markedly reduced although its permeability was normal. The membrane tortuosity factors for thiopental were also reduced. These facts indicate the existence of multiple diffusive pathways for thiopental and its exclusion from some solvent pathways in the membranes studied. © 1979 American Chemical Society.