The clustering of nanoparticles (NP) within solutions and polymer melts depends sensitively on the strength and directionality of the NP interactions involved, as well as the molecular geometry and interactions of the dispersing fluids. Since clustering can strongly influence the properties of polymer-NP materials, we aim to better elucidate the mechanism of reversible self-assembly of NP into clusters under equilibrium conditions. We perform molecular dynamics simulations of icosahedral NP with a long-ranged interaction intended to mimic the polymer-mediated interactions of a polymer-melt matrix. To distinguish effects of polymer-mediated interactions from bare NP interactions, we compare the NP assembly in the coarse-grained model to the case where the NP interactions are purely short-ranged, both with and without an explicit polymer matrix. For the control case of NP with the short-ranged interactions and no polymer matrix, we find that the particles exhibit phase separation.By incorporating long-ranged interactions we qualitatively reproduce the thermally reversible cluster formation found previously in computations for NP with short ranged interactions in an explicit polymer melt matrix. This series of simulations shows that we can mimic NP-polymer melt interactions through the introduction of a simple effective potential having a long-ranged interaction. This coarse-grained approach to simulating NP in a polymer matrix should be helpful in exploring factors that control the dispersion of NP in polymer matrices where explicit simulation of the polymer matrix is too time consuming.
Citation: Journal of Chemical Physics
Pub Type: Journals
diffusion, effective potential, many-body interactions, nanocomposite, particle dispersion, phase separation, reversible clustering transition, self-assembly