HINDERED DIFFUSION OF WATER-SOLUBLE MACROMOLECULES IN MEMBRANES

The diffusion coefficients of four water-soluble macromolecules were determined in membranes containing pores having dimensions comparable to those of the solutes. The effective diffusion coefficients of ficoll, a highly cross-linked polysaccharide, were in excellent agreement with those predicted by a hydrodynamic theory for a solid, spherical solute. Effective diffusion coefficients for linear poly(ethylene oxide)(PEO) were between those predicted for a solid sphere and for a flexible, linear polymer. In contrast, linear poly(vinylpyrrolidone) (PVP) and nearly linear dextran diffused through the membranes more rapidly than predicted by either theory.