(495f) Multiscale Modeling of Polyisoprene On Silica and Graphite

Materials created by dispersing nanoparticles in a polymer matrix strive to meet the promise of enhanced and often unique properties at a reduced cost. The availability of structure-property relationships and predictive modeling are deemed necessary to tailor these materials according to our needs. Molecular dynamics simulations of polymer-particle mixtures in atomistic detail is limited by exceedingly large systems required to be probed over the longest-relaxation time of the polymer on the surface.

In this study we examine the ability of systematically derived-coarse grain models (CG) to probe the configurations of cis-1-4 polyisoprene (PI) in proximity to silica and graphite surfaces. All atom (AA) molecular dynamic simulations of large systems are performed and details of chain configurations are extracted. Using the Iterative Boltzmann Inversion method¹ we construct interaction potentials between CG segments as well as between polymer segments and flat surfaces. We find that in the melt state, CG models can quantitatively describe the structure of the melt as verified by detailed comparison with AA models. We propose a scheme to extract interaction potentials between a nanoparticle and PI based on our calculations with flat surfaces. We find that with our approach we can capture accurately the melt structure around curved nanoparticles without the need of further optimization of the interaction parameters. Subsequently, we employ recently developed Monte Carlo algorithms that couple connectivity-altering moves with preferential sampling.² Our approach allows the accurate characterization of the polymer layer surrounding nanoparticles without current limitations imposed by chain-connectivity. Finally we discuss extensions of our work on extracting the interactions between two particles immersed in a polyisoprene matrix.

1. D. Reith, M. Putz, F. J. Müller-Plathe, J. Comput. Chem., 24, 1624–1636, 2003.

2. Y. Pandey and M. Doxastakis, , J. Chem. Phys., 136, 094901, 2012.