Preparation and Swelling Behavior of Chitosan/Poly(N-2-Aminoethyl Acrylamide) Composite Hydrogels

Chitosan-based composite hydrogels covalently cross-linked were obtained by mixing, in different proportions, chitosan (CS) and poly(N-2-aminoethyl acrylamide) (PAEA), both polycations containing primary amine groups in the side chain able to react with glutaraldehyde (GA) as cross-linker. The swelling ratio of composite hydrogels increased with about 50% when the PAEA:CS molar ratio increased from 0.11 up to 3.54, at a constant concentration of polycations. A linear relationship between the equilibrium swelling and the nominal cross-linking degree, expressed as moles GA/100 moles NH2, at both pH 2 and 5.5 was observed. To get information about the swelling mechanism, the diffusion phenomena were analyzed by the empirical equation Franson and Peppas. The values of n < 0.5 showed that the water sorption in the composite gels, at pH 5.5, was more diffusion- than relaxation-controlled.