Effect of Particle Size on the Swelling and Compression Modulus of Nanostructured Polyacrylamide Hydrogels

The effects of concentration and size of polyacrylamide (PAM) nanoparticles on the swelling behavior and compression modulus of nanostructured polyacrylamide hydrogels are examined here. These hydrogels are made by free radical polymerization in an aqueous solution of acrylamide and a crosslinking agent containing dispersed crosslinked PAM nanoparticles of different sizes, previously made by inverse emulsion or microemulsion polymerization. Faster swelling rate and larger equilibrium swelling are observed as particle content increases or the nanoparticle size diminishes. The compression modulus depends on the concentration and size of the disperse nanoparticles: it is larger for hydrogels containing smaller particles at similar concentrations, and it increases as the nanoparticle concentration augments. Moreover, the nanostructured hydrogels have larger compression modulus than those of the conventional ones having similar swelling.