Membranes with varying degree of crosslinking and ionic content were prepared from interpenetrating networks of poly(vinyl alcohol) and poly(acrylic acid). Equilibrium swelling studies were conducted to characterize their crosslinked structure and determine the average molecular weight between crosslinks, crosslinking density, and mesh size of the networks. Equilibrium and oscillatory swelling studies were performed to investigate the gel response to changes in the pH and ionic strength of the swelling medium, The permeation of solutes of varying size including urea, guaiacol glyceryl ether, L-tryptophan, vitamin B-12 and selected dextrans was investigated as a function of pH and membrane mesh size.