Some mechanical properties of poly[(acrylic acid)-co-(itaconic acid)] hydrogels

Two series of hydrogels of poly[(acrylic acid)-co-(itaconic acid)] have been prepared by copolymerization in solution using tetrafunctional N,N'-methylenebisacrylamide (NMBA) as cross-linker. The resulting polymer was swollen in water at 298 K to yield homogenous transparent hydrogels. These hydrogels were characterized in terms of swelling and compression-strain measurements. The influence of the comonomer composition and concentration of cross-linking agent on volumetric swelling and the mechanical properties of these hydrogels were investigated. Inefficient cross-linking is indicated by the small values of v(e) relative to the theoretical cross-linking densities. Dependence of measured affective cross-linking density (v(e)) on the theoretical cross-linking density (v(t)) for acrylic acid/itaconic acid hydrogels prepared at a fixed composition of AA80/A120 wt.-% but at different concentrations of NMBA.