Investigation of the Structure and Dynamics of Polyethylene Nanocomposites

The structure and dynamics of linear, monodisperse polyethylene (PE) melts (C$_{160}$H$_{322}$ and C$_{440}$H$_{882}$) containing homogenously distributed spherical nanoparticles were investigated. The PE chains were simulated using a coarse grained model and a Monte Carlo algorithm. Two variables were considered: (i) the wall-to-wall distance between particles (\textit{d}), and (ii) the interaction energy between monomers and particles. The various chain structures changed greatly with \textit{d} while the monomer-particle interaction had little effect. The average size, shape, and orientation of PE chains did not differ significantly from those of a neat melt. Bridge segments were more stretched relative to segments in the neat melt and the stretch increased with increasing \textit{d}. However, the number of bridge segments decreased markedly with increasing \textit{d}. Chain dynamics was monitored by computing the Rouse relaxation modes and the mean-square displacement of the center of mass. The dynamics were slowed by both geometric effects (confinement by fillers) and energetic effects (monomer-particle energetic interaction).