Tailoring the mechanical properties of polyacrylamide-based hydrogels

Here, we studied the mechanical properties of polyacrylic acid-co-polyacrylamide (pAAc/pAAm) and polyacrylate-co-polyacrylamide (pNaAc/pAAm)-based hydrogels as a function of composition and total polymer content. While both polyacrylate and polyacrylic acid are weakly-charged polyelectrolytes with carboxylate side groups, they exhibit different behavior as copolymers with polyacrylamide. In swelling studies the highest degree of volumetric expansion occurs in the polyacrylate-rich hydrogels. Rheological measurements indicate that the shear storage modulus of the hydrogels typically increases with the percentage of polyacrylamide for a given polymer volume fraction; however, the simultaneous strengthening and embrittling effects of polyacrylamide as a copolymer are more dramatic for the pNaAc/pAAm hydrogels.