Multiscale modeling of polyisoprene on graphite

Abstract

The local dynamics and the conformational properties of polyisoprene next to a smooth graphite surface constructed by graphene layers are studied by a multiscale methodology. First, fully atomistic molecular dynamics simulations of oligomers next to the surface are performed. Subsequently, Monte Carlo simulations of a systematically derived coarse-grained model generate numerous uncorrelated structures for polymer systems. A new reverse backmapping strategy is presented that reintroduces atomistic detail. Finally, multiple extensive fully atomistic simulations with large systems of long macromolecules are employed to examine local dynamics in proximity to graphite. Polyisoprene repeat units arrange close to a parallel configuration with chains exhibiting a distribution of contact lengths. Efficient Monte Carlo algorithms with the coarse-grain model are capable of sampling these distributions for any molecular weight in quantitative agreement with predictions from atomistic models. Furthermore, molecular dynamics simulations with well-equilibrated systems at all length-scales support an increased dynamic heterogeneity that is emerging from both intermolecular interactions with the flat surface and intramolecular cooperativity. This study provides a detailed comprehensive picture of polyisoprene on a flat surface and consists of an effort to characterize such systems in atomistic detail.

Dynamics heterogeneity in silica‐filled nitrile butadiene rubber

“…In silica‐filled NBR, the glassy layer maintained by dipole–dipole interaction is very thin (0.1–0.5 nm). Surrounding this layer, the loop‐rich subchains with a distribution of contact lengths form sublayers where the segmental dynamics are forbidden and the transport of the chain mass center deviates from the glassy behavior . At larger distances, the bound subchains become more diffuse due to prevailing of tails, and the loops force the tails to nonuniformly extend away from the inner sublayer to behave akin to “polydisperse pseudobrushes.” In the silica‐filled NBR, glassy layers are clearly detected by MDSC, as well as ARF and an unvaried or slightly accelerated mobile fraction by BDS.…”

Hierarchical modelling of polystyrene melts: from soft blobs to atomistic resolution

“…We emphasize that the method is not restricted to polystyrene and can be straightforwardly applied to equilibrate melts of other polymeric materials, where moderately CG models exist. [11,[59][60][61][62][63] Appendix: "push-off " procedure for backmapping the blob-based model to the chemically specific coarse-grained model…”

Multiscale Molecular Simulations of Polymer-Matrix Nanocomposites

“…Pandey et al [ 245 ] have extensively studied the local dynamics and the conformational properties of polyisoprene next to a smooth graphite surface constructed by graphene layers, via a multiscale simulation methodology. These authors first performed fully atomistic molecular dynamics simulations of isoprene oligomers, next to the surface.…”

“…b Average dynamics of repeat units on graphite along a train segment as a function of the length of it. (Color figure online) (Reprinted from [ 245 ], with the permission of AIP Publishing.) …”

“…Figure 22 presents a qualitative visual inspection of the distribution of times for a specific configuration. Pandey et al [ 245 ] evaluated an autocorrelation function individually for every c-CH vector and colored each segment from blue to red signifying lower relaxation times and higher mobility. As shown, segments in proximity to the surface were found to be slower.…”