Water sorption dynamics of a binary copolymeric hydrogel of 2-hydroxyethyl methacrylate (HEMA).

The water imbibing property of poly(2-hydroxyethyl methacrylate) (poly HEMA) has been improved by copolymerizing HEMA with acrylamide in the presence of a hydrophilic polymer such as polyethylene glycol (PEG). The hydrogel was characterized by IR spectral analysis and several network parameters such as average molecular weight between crosslinks (Mc), crosslink density (q) and number of elastically effective chains were evaluated. The swelling ratio of the hydrogel was found to be influenced by varying the chemical architecture of the hydrogel, i.e. by changing the proportions of PEG, HEMA, acrylamide and crosslinking agent in the feed mixture of the hydrogel. The degree of water sorption was studied as a function of the experimental conditions such as the pH and temperature of the swelling medium and presence of salt ions in the outer solution. The dynamics of the swelling process was studied quantitatively and kinetic constants such as the swelling exponent (n) and diffusion constant (D) were also evaluated. The hydrogels prepared of varying composition were judged for antithrombogenic nature of their surfaces by blood-clot formation test.