Preparation and characterization of pH‐sensitive, interpenetrating networks of poly(vinyl alcohol) and poly(acrylic acid)

Abstract

Abstract Hydrogels with varying cross‐linking ratio and ionic content were prepared from interpenetrating networks of poly(vinyl alcohol) and poly(acrylic acid). Equilibrium swelling studies were conducted and the average molecular weight between cross‐links, M c , and mesh size were determined. Hydrogels with large M c , values were found to swell to a greater extent than those with small M c values. It was also observed that an increase in M c yielded faster swelling and deswelling rates, as the rates for membranes with M c = 18,000 were about twice as fast as were the rates for membranes with M c = 34,000. Oscillatory swelling behavior was investigated in response to changes in the pH and ionic strength of the swelling medium. A change in pH from 3 to 6 caused an ionization of the hydrogels and an increase in the weight swelling ratio, with a greater increase exhibited by IPNs with a higher ionic content. Increase in pH also caused an increase in the average mesh size. © 1995 John Wiley & Sons, Inc.