Molecular Insights into the Mechanical Behavior of Single and Multi-component Polymer-Grafted Nanoparticles

Polymer-grafted nanoparticles (PGNs) exhibit remarkable mechanical properties due to the synergy between their stiff nanoparticle (NP) cores and flexible polymer coronas. Recent experimental studies have demonstrated enhanced elasticity, energy absorption, and the creation of highly ordered multi-PGN superlattices. However, their relationship with PGNs’ design parameters and the underlying deformation mechanisms are poorly understood. In this talk, I will present a chemistry-specific coarse-grained (CG) molecular modeling framework to address these knowledge gaps.

We simulated the micro-ballistic response of PGN monolayers, where we found that inter-PGN cohesive energy density positively influences energy absorption. Importantly, intermediate graft lengths (no. of monomers = 40-100) offer an optimal balance between energy absorption and resistance to compression, which is ideal for designing impact-resistant materials with minimal backface deformation. Next, we examined the shear modulus of PGNs and discovered a linear relationship between the NP volume fraction and modulus. Furthermore, we have constructed multi-component PGNs with varying NP core sizes and graft densities, reproducing experimentally observed superlattice structures. Our results indicated that binary mixtures of PGNs outperform single-component systems, likely due to more efficient packing at the nanoscale. We integrated these findings into an ML-based model correlating deformation data and PGNs’ design parameters. Finally, we developed an implicit chain CG model that represents PGNs as single particles, which achieves a 10⁷ speed-up over all-atom models while capturing bulk modulus and toughness. This lays the foundation for mesoscale simulation to understand fracture behavior from a molecular standpoint.

Ultimately, the framework enables us to explore the design parameters of single and multi-component PGNs efficiently and create a molecular-level understanding of deformation mechanisms. This will lead to the creation of high-performance PGNs with simultaneously higher strength and toughness, which is critically needed to reduce the consumption of single-use plastics.