Toughening glassy polymer-grafted nanoparticle systems via interdigitation and entanglement mechanics

The assembly of polymer-grafted nanoparticles (PGNs) into matrix-free nanocomposites offers a unique method for designing materials with tailored properties, leveraging the combined attributes of nanoparticles and polymers in ways that surpass the capabilities of either component alone. This work employs coarse-grained molecular dynamics simulations to systematically investigate how key PGN design parameters, such as grafted chain length, grafting density, and nanoparticle size, affect the mechanical performance of glassy PGN systems. At high nanoparticle volume fractions, the systems exhibit increased stiffness but a corresponding reduction in toughness. At similar nanoparticle volume fractions, systems containing larger nanoparticles, longer grafted chain lengths, and low grafted densities exhibit greater toughness. The combination of these parametric attributes enables enhanced interdigitation between neighboring PGNs. Finally topological analysis reveals a key mechanism driving high strain hardening in these systems is the survival of effective inter-PGN entanglements, which can enable sustained energy dissipation in the large deformation regime.