Soft Nanoparticles as Adhesives for Gel-like Materials

It is known that nanoparticles can act as effective adhesives for soft polymeric materials. Using a combination of molecular dynamics simulations and theoretical calculations, we study the ability of soft nanoparticles to glue together gel-like surfaces. In particular, we have shown that at the interface between two gel-like surfaces nanoparticles can be in a bridging state, Pickering state, or engulfed state. The depth of indentations produced by nanoparticles into soft substrates is controlled by nanoparticle size, nanoparticle and substrate Young’s modulus, and their surface properties. Using molecular dynamics simulations, we have elucidated relationships between deformations of the nanoparticles and substrates and their elastic and surface properties. By varying moduli of nanoparticles and gel-like substrates, we find that it is possible to observe a coexistence of both bridging state and Pickering state. Furthermore, we use the Weighted Histogram Analysis Method to calculate the work required for separation of two gels which interface is reinforced by nanoparticles. To explain our simulation results, we have developed a model relating the work of substrate separation with the physical parameters describing contact phenomena in nanoparticle/substrate systems.