Stractural and Dynamical Properties of Hybrid Polymer/Gold and Core-Shell Nanoparticle Systems through Molecular Dynamics Simulations*

We present a detailed investigation of polymer nanocomposites (PNCs) with a bare and functionalized nanoparticle (NP) via detailed atomistic molecular dynamics (MD) simulations. Our model systems consist of polyethylene (PE) matrix with dispersed bare or functionalized gold (Au) NPs. We probe the structural and dynamical properties of polymer chains in the PNCs focusing on the PE/Au interphase. An oligomeric PE matrix with 22 monomers per chain and a Rouse-like one with 100 monomers per chain are examined. Also different model gold NPs, using the Wulff construction, with a diameter from 2.5 nm up to 5.0 nm, are considered. The grafting density for the core-shell NP systems is 0.67 chains/nm². We examined properties of the PE chains as a function of the distance from the Au NP. That allow us to examine the way spatial and dynamical heterogeneities are related to the molecular structure, in particular at the vicinity of the PE/Au interphase. Results concerning polymer density profiles, bond order parameter, segmental and terminal dynamics show that the size of the interface/interphase, depends on the actual property under study. In addition, the anchored polymeric chains change the behavior/properties of the polymer chains, and especially the chain density profile and the dynamics, at the vicinity of the Au NP.