Nanoparticle Dispersion and Hierarchical Structure in Polymer Nanocomposites: Insights from Dissipative Particle Dynamics (DPD) Simulation*

In polymeric systems such as natural rubber, nanoscale fillers are widely employed as cheap and effective additions for enhanced properties and functionality. Such nanocomposites may contain fillers of varying miscibility, such as carbon black, silica, pigments, metal oxides and/or various combinations thereof. In such systems, a complex partitioning of the components often results from the rich thermodynamics and kinetic history. The state of dispersion of the polymers and fillers is challenging and crucial to the behavior of nanocomposites. In this research, we perform Dissipative Particle Dynamics (DPD) simulation of these blends, varying polymer-polymer interaction energy, to understand the hierarchical structure and dispersion over multiple length and timescales. These results are validated against small-angle x-ray scattering to bridge a significant gap in our understanding of how complex hierarchical structure develops. Additionally, our results demonstrate the role of concentration on the clustering of fillers, investigated via the cluster size, radius of gyration, and the population distribution. It also demonstrates the formation of large percolating aggregates and can be mapped onto the macroscopic percolation characterized by rheology.