New hydrogels based on the interpenetration of physical gels of agarose and chemical gels of polyacrylamide

In this paper we report a novel method for preparing interpenetrating polymer hydrogels of agarose and polyacrylamide (PAAm) in three steps. The procedure consists in (i) formation of physical hydrogels of agarose, (ii) diffusion of acrylamide, N,N-methylene-bis-acrylamide and potassium persulfate (the initiator) from aqueous solutions inside the gel of agarose, and (iii) cross-linking copolymerization reaction of the aforementioned reactants to produce PAAm chemical gels interpenetrated with the agarose physical gels. Viscoelasticity measurements and thermal analysis have been performed in order to follow the kinetics of copolymerization. The viscoelastic, swelling and thermal properties of the resulting hydrogels confirm the formation of an interpenetrated system. Further evidence of interpenetration is obtained from inspection with atomic force microscopy. The improvement of the agarose and PAAm gel properties in the resulting interpenetrated hydrogel is analyzed in view of the results. (C) 2008 Elsevier Ltd. All rights reserved.