Hindered diffusion of flexible polymers through polyimide ultrafiltration membranes

Abstract

ABSTRACT:The hindered diffusion of polystyrene in dilute solutions of ethyl acetate through polyimide ultrafiltration membranes has been investigated. The present system did not show specific membrane-solute interactions; furthermore, polystyrene can be considered as a flexible polymer coil. It is shown that the hindered diffusive permeability for monodisperse dilute solutions for a series of molecular weights can be compared well with the diffusive permeability curve of one polydisperse dilute polystyrene solution. In the case of very dilute solutions, the polymer coils have no interaction with each other, and the whole range of molecular-weight-dependent permeabilities can be determined from only one measurement. The diffusion behavior of polydisperse solutions through various polyimide membranes has been investigated as well. It was found that the diffusive permeability curve is strongly dependent on the type of membrane, that is, on the pore size distribution. It was not possible to calculate a pore size distribution from diffusion experiments due to mathematical limitations. Nevertheless, it was shown that hindered diffusion measurements are useful to estimate a maximum pore size for each membrane.

Diffusion of semi‐flexible polyelectrolyte through nanochannels

“…Our results were also compared with literature measurement on the same type of track‐etch membrane with similar pore sizes 28, 29. The membrane boundary layer effect can also be estimated by analytical method,30 given that the membrane used here has very low porosity and the diffusion experiments were conducted under sufficient stirring.…”

Special Features of Crazing of Glassy Poly(ethylene terephthalate) in Poly(ethylene oxide) Solutions

“…It is assumed that the mass transfer of macromolecules inside the nanopores from dilute solutions occurs via the translation mechanism, and the coil hydrodynamic radius R h is a parameter of crucial importance. Polymer coils are considered hard spheres in the dilute solution, and their diffusion-driven (no external force) penetration in the pores is possible when the coil hydrodynamic radius does not exceed the pore size ( r p ), R h ≤ r p . The macromolecule penetration in the smaller pores is only possible under external force action, when the solvent flow exceeds certain critical value .…”

“…Polymer coils are considered hard spheres in the dilute solution, and their diffusion-driven (no external force) penetration in the pores is possible when the coil hydrodynamic radius does not exceed the pore size (r p ), R h ≤ r p . 18 The macromolecule penetration in the smaller pores is only possible under external force action, when the solvent flow exceeds certain critical value. 17 This threshold flow value is determined by a balance of friction between macromolecules and solvent and the elastic returning force of the polymer coil.…”

Nanoporous materials for biomedical devices

“…Experimental evaluation of these theories has been difficult because the pores in traditional membranes are far from ideal, since they exhibit a wide range of pore size distributions as well as a random network of pores. 21 Recent studies have examined polymer diffusion in well-defined and ordered pores. 22 The use of nanoporous membranes with well-ordered capillary pores is particularly attractive in size sorting and molecular analysis applications.…”