Hydrodynamic Permeability of Hydrogels Stabilized within Porous Membranes

The purpose of this work was to demonstrate that cross-linked polymer gels can be stabilized against mechanical and osmotic forces by confining them in a microporous support. The hydrodynamic (Darcy) permeability was measured for neutral and charged polyacrylamide (PA) gels synthesized in semirigid membranes having a hydraulic mean pore diameter of 0.5 μm and a porosity of 67%. The permeability was determined by measuring the flow rate of aqueous solutions as a function of pressure drop across the membranes. The membrane-supported gels were stable and yielded a constant permeability when the pressure drop was increased to 300 bar/cm. No swelling/deswelling was observed with the charged gels (0.3−0.4 equiv/L) when the ionic strength was varied between 0.01 and 1.0 M, and the permeability was essentially independent of ionic strength. The permeability of the neutral gel varied as φ - 3.3 where φ is the polymer volume fraction, whereas literature data for bulk PA gels shows the dependence to be φ - 1.4 . The permeability of the membrane-supported neutral PA gel was greater than the literature values for the bulk gel at low φ but comparable to the bulk gels when φ > 0.08.