Polyacrylamide (PAAm)-based hydrogels covalently bonded to a polypropylene (PP) substrate have been synthesized using modification of the PP with a new functional polyperoxide (FPP). The FPP initiates radical polymerization from the PP's surface by decomposing the peroxide groups. Two different approaches for forming the hydrogel network have been used. In the first, a grafted hydrogel network is formed by radical polymerization of the acrylamide on the peroxidized PP substrate ("grafting from") in the presence of N,N'-methylene-bis-acrylamide (a cross-linking agent) and potassium persulfate (an additional initiator in bulk). In the second approach, a grafted hydrogel network is synthesized by: (i) grafting the PAAm macromolecules from the peroxidized PP substrate and (ii) following intermolecular condensation of the surface-grafted PAAm and adding to the reactive bulk PAAm and poly-N-(hydroxymethyl)acrylamide (used as a cross-linking macromolecule). resulting in the formation of a hydrogel network grafted to the PP substrate. The covalent attachment of hydrogel networks has been verified for both approaches by contact angle measurements, dye adsorption by the hydrogel residues after network removal and extraction, and mechanical failure tests. The intermolecular condensation method has been found to be more advantageous for the formation of covalently bonded hydrogels on the PP substrate, while grafted network formation by radical polymerization was detected only for a limited range of monomer and cross-linking agent concentrations. (C) 2010 Elsevier Ltd. All rights reserved.