Permeability of dilute polyacrylamide hydrogels

Permeability of dilute (containing 1 to 4 wt % of polymer) homogeneous polyacrylamide hydrogels to globular proteins, microspheres of polysilicic acid, and restricted fragments of double-strand DNA were studied by diffusion, quasielastic laser light scattering, and electrophoresis. By analyzing the mobility of penetrating particles for all three penetrating species, pore dimensions of the hydrogels were evaluated. It was found that diffusion mobility of compact particles in the examined hydrogels is controlled mostly by the characteristic size of the fluctuation network of entanglements rather than by the size of the cell of chemical network, which is specified during the synthesis by the amount of cross-linking agent. The sizes of the cell evaluated from DNA electrophoresis (860 - 1120 Angstrom) and protein diffusion (80 - 180 Angstrom) were found to be significantly different. The causes of this discrepancy are discussed.