Coarse Graining Atactic Polystyrene and its Analogues

Capturing large length scales in polymers and soft matter while retaining atomistic properties is imperative to computational studies of dynamic systems. Coarse graining the explicit atomistic description of polymers into larger beads is one critical tool that can bridge atomistic simulations with the mesoscopic length scale, enabling the study of polymer properties. Here we present a new coarse-grain methodology based on a single all-atom simulation of a polystyrene (PS) melt. Similar to previous work by Fritz et al., each PS monomer is described by two coarse grained beads. However, in contrast to this earlier work, where intramolecular potentials were based on Monte Carlo simulation of both isotactic and syndiotactic single polystyrene (PS) molecules to capture stereochemistry, both the inter and intramolecular interactions are obtained from a molecular dynamics simulation of an atactic PS melt.1 This new potential captures well the density of PS as a function of molecular weight as measured experimentally. Thus, this 2:1 CG model presents an immense improvement over previous studies since it captures the stereochemistry of the polystyrene. These CG models can be back-mapped to the atomistic structure. With this successful model, we provide new insights into impacts of interfacial roughness on diffusion.