PORE-SIZE DISTRIBUTIONS OF CATIONIC POLYACRYLAMIDE HYDROGELS VARYING IN INITIAL MONOMER CONCENTRATION AND CROSS-LINKER - MONOMER RATIO

Pore-size distributions have been measured for cationic acrylamide-bas ed hydrogels. We use the experimental mixed-solute-exclusion method, M SE (introduced by Kuga), to obtain the solute-exclusion curve represen ting the amount of imbibed liquid inside the gel inaccessible for a so lute of radius r. We use the Brownian motion model (developed by Cassa sa) to convert the size-exclusion curve into the pore-size distributio n, which gives the frequency of pore radius R as a function of R. This theoretically-based interpretation of MSE data leads to the Fredholm integral equation that we solve numerically. Results are reported for a series of hydrogels containing acrylamide and 3% MAPTAC; the hydroge ls differed in extent of cross-linking and/or initial concentration of monomer. Pore-size distributions shift to lower pore sizes with risin g initial monomer concentration and with rising cross-linker-to-monome r ratio.