Theoretical Reconstruction of Realistic Dynamics of Highly Coarse-Grained cis-1,4-Polybutadiene Melts

TL;DR

This paper develops a theoretical method to accurately reconstruct atomistic-level polymer dynamics from mesoscale simulations of coarse-grained cis-1,4-polybutadiene melts, bridging different scales with good agreement to detailed simulations.

Contribution

It introduces a formalism that corrects mesoscale simulation data for entropy and friction changes, enabling realistic atomistic dynamics reconstruction from coarse-grained models.

Findings

Rescaled diffusion coefficients match atomistic simulation data.

The theory accurately predicts time correlation functions across scales.

The approach requires only static quantities as input.

Abstract

The theory to reconstruct the atomistic-level chain diffusion from the accelerated dynamics that is measured in mesoscale simulations of the coarse-grained system, is applied here to the dynamics of cis-1,4-Polybutadiene melts where each chain is described as a soft interacting colloidal particle. The rescaling formalism accounts for the corrections in the dynamics due to the change in entropy and the change in friction that are a consequence of the coarse-graining procedure. By including these two corrections the dynamics is rescaled to reproduce the realistic dynamics of the system described at the atomistic level. The rescaled diffusion coefficient obtained from mesoscale simulations of coarse-grained cis-1,4-Polybutadiene melts shows good agreement with data from united atom simulations performed by Tsolou et al. The derived monomer friction coefficient is used as an input to the theory for cooperative dynamics that describes the internal dynamics of a polymer moving in a transient regions of slow cooperative motion in a liquid of macromolecules. Theoretically predicted time correlation functions show good agreement with simulations in the whole range of length and time scales in which data are available. The theory provides, from data of mesoscale simulations of soft spheres, the correct atomistic-level dynamics, having as solo input static quantities.