Analysis of the complexation/decomplexation phenomena in graft copolymer networks

Graft copolymer networks of poly(methacrylic acid-g-ethylene glycol) exhibiting pH-dependent swelling behavior due to the formation of interpolymer complexes were prepared by free radical solution polymerization of methacrylic acid and poly(ethylene glycol) monomethacrylate. Dynamic swelling studies established the swelling/deswelling process due to hydrogen bonding. Additionally, the effects of copolymer composition, graft chain molecular weight, and environmental pH on network structure were studied. The average network correlation length changed significantly due to changes in environmental pH. The largest changes in network structure were observed in gels containing nearly equimolar amounts of methacrylic acid and ethylene glycol and the longest molecular weight poly(ethylene glycol) grafts. Water diffusion coefficients, determined through dynamic swelling analysis, varied by 2 orders of magnitude between the uncomplexed and complexed states.