Lattice Monte Carlo simulations of chain conformations in polymer nanocomposites

Lattice Monte Carlo simulations were performed on monodisperse polymer melts, with DP's ranging from 100 to 400, filled with nanoparticles of sizes comparable to the chain R, We critically study the role of the mean distance between these nanofillers on the overall conformation of polymer chains and, more importantly, on the statistics of bridges, dangling ends, loops, and trains. We are motivated to study these issues since it has been suggested that the mechanical behavior of nanocomposites result from the formation of a long-lived transient filler network mediated by the chains. Further, the experimentally observed increase in low frequency, low strain amplitude elastic modulus on the addition of filler is attributed to strongly stretched bridge segments. We find that the overall chain statistics remain Gaussian regardless of filler loading (up to 27 vol %). Short bridges, loops, and tails are strongly stretched, but in a manner that is quantitatively equivalent to the statistics of subchains in a melt. These results unequivocally assert that nanoparticles do not affect equilibrium melt chain conformations and that this idea can underpin the development of new models for polymer nanocomposites.