Finite elasticity of nanocomposite hydrogels

Constitutive equations are derived for the elastic response of nanocomposite hydrogels subjected to swelling under an arbitrary deformation with finite strains. Under rapid deformation of as-prepared specimens, the stress-strain relations involve four adjustable parameters that are found by fitting observations on poly(N-isopropylacrylamide), poly(N,N- dimethylacrylamide), and polyacrylamide hydrogels reinforced with Laponite nanoclay and graphene oxide. Good agreement is demonstrated between the observations and the results of numerical simulation at elongations up to 3000%. A pronounced difference is revealed between the effect of filler content on material parameters of chemical and physical nanocomposite gels.