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 confin ing them in a microporous support. The hydrodynamic (Darcy) permeabili ty was measured for neutral and charged polyacrylamide (PA) gels synth esized in semirigid membranes having a hydraulic mean pore diameter of 0.5 mu m and a porosity of 67%. The permeability was determined by me asuring the flow rate of aqueous solutions as a function of pressure d rop across the membranes. The membrane-supported gels were stable and yielded a constant permeability when the pressure drop was increased t o 300 bar/cm. No swelling/deswelling was observed with the charged gel s (0.3-0.4 equiv/L) when the ionic strength was varied between 0.01 an d 1.0 M, and the permeability was essentially independent of ionic str ength. The permeability of the neutral gel varied as phi(-3.3) where p hi is the polymer volume fraction, whereas literature data for bulk PA gels shows the dependence to be phi(-1.4). The permeability of the me mbrane-supported neutral PA gel was greater than the literature values for the bulk gel at low phi but comparable to the bulk gels when phi > 0.08.