Nanoparticles Organization Controls Their Potency as Universal Glues for Polymer Interfaces.

In recent years, nanoparticles (NP) have been shown to have the potential to answer the centuries-old question of how to mechanically strengthen an interface between soft materials. The wide range of tuneable parameters and properties make glues composed of nano-sized particle appealing to a variety of fields and applications. The design of new adhesive, however, would benefit from a deeper understanding of the parameters that concur to determine the final adhesion strength. We used a coarse-grained model of polymer melts and nanoparticles, and molecular dynamics simulations to shine light on the interplay of three key properties, namely NP size, NP-polymer interaction strength, and NP density. Our main result shows a non-monotonous strengthening of the mechanical response depending on the nanoparticle concentration at the interface. Furthermore, our findings are in good qualitative agreement with a simple analytical model of the melt adhesive energy that we developed. The results from this investigation help disentangling the contributions to the strengthening of the interface and can be used as a guide to experimental design of nanoparticles-based adhesives.