Graft polymerization of acrylic acid onto macroporous polyacrylamide gel (cryogel) initiated by potassium diperiodatocuprate

Potassium diperiodatocuprate-initiated graft polymerization was found to be an efficient and convenient method for grafting of acrylic acid (AAc) onto superporous polyacrylamide gels, so called cryogels (pAAm cryogels). It was possible to achieve grafting degrees as high as 70% with about 25% yield of grafted polymer with respect to the initial amount of monomer. The superporous structure of the cryogels promoted grafting by providing an ample surface of the gel for grafting, ensuring good mass transfer inside the gel sample and allowing to wash easily both homopolymer of AAc and insoluble by-products formed during the polymerization reaction. The grafted cryogels could be dried at 60 °C and re-swollen with retaining their properties. The adsorption of water vapours by dried pAAm cryogels was marginally dependent on the degree of grafting. The swelling of AAc-grafted pAAm cryogel increased pronouncedly with increasing pH. The adsorption of low-molecular weight ligand, Cu(II), by AAc-grafted pAAm cryogels increased linearly with the degree of grafting, while binding of high-molecular weight ligand, lysozyme, increased linearly till the degree of grafting of about 40% followed by a sharp, nearly three-fold increase in lysozyme binding when the degree of grafting increased from 60 to 70%. The results indicate that a 'tentacle'-type binding of lysozyme to grafted polyAAc takes place after a certain degree of grafting has been reached.