Investigation of Dialysis Membrane Transport Properties by Use of NMR Relaxation and Diffusion Measurements Coupled to Transport Models

Proton NMR T₁ and T₂ relaxation times are analyzed for bundles of polysulfone hemodialyzer membranes in contact with water. A diffusion-reaction model with volumetric and surface sinks is used in conjunction with known fiber geometries to explain observed relaxation trends. Surface relaxation strengths are determined for temperatures between 278-348 K for both spin-lattice (T₁) and spin-spin (T₂) relaxation mechanisms. Inferred surface relaxation strengths based on T₂ were ~100 times greater than those based on T₁. Surface relaxation strength decreased with temperature indicating that relaxation is dominated by dipolar coupling for this material. Because the chemical structure of polysulfone contains no exchangeable hydrogen's, observed surface relaxation strengths are consistent with the idea that the material surface interacts with water by way of dipolar interactions. Future work will test materials with different modes of interaction with a solvent using current experimental methods to establish the validity and utility of the approach.