In this study, fracture toughness of nanocomposite
hydrogels is quantified, and active mechanisms for dissipation
of energy of nanocomposite hydrogels are ascertained.
Poly(N,N-dimethylacrylamide) nanocomposite hydrogels are
prepared by in situ free radical polymerization with the incorporation
of Laponite, a hectorite synthetic clay. Transmission
electron microscopy proves exfoliation of clay platelets that
serve as multifunctional crosslinkers in the created physical
network. Extraordinary high fracture energies of up to 6800
J m22 are determined by the pure shear test approach, which
shows that these soft and stretchable hydrogels are insensitive
to notches. In contrast to single- and double-network hydrogels,
dynamic mechanic analysis and stress relaxation experiments
clarify that significant viscoelastic dissipation occurs
during deformation of nanocomposite hydrogels. Similar to
double-network hydrogels, crack tip blunting and plastic deformation
also contribute to the observed massive fracture energies.