Assortative nanoparticle percolation in nanocomposite gels

The addition of sticky nanoparticles in a physically associated hydrogel matrix is considered. It is shown that the nanoparticles assortatively self-assemble into a percolated nanoparticle network at volume fractions far below the percolation threshold of a pure sticky nanoparticle hydrogel. Concurrently, it is shown that hydrogel undergoes substantial mechanical reinforcement, as manifested by the emergence of a low-frequency plateau in the viscoelastic shear moduli as determined via rheology, and the increased elastic moduli as determined via cavitation. Nanoparticles added beyond the percolation threshold are shown to bolster the connectivity of the percolated nanoparticle network, as revealed by mechanical measurements as well as structure factor calculations. These results provide fundamental insights into the self-assembly, and mechanical consequences therein, of multicomponent reversible hydrogels.