Dynamic coarse-graining of polymer systems using mobility functions

TL;DR

This paper introduces a novel dynamic coarse-graining method for polymer systems that uses wave-vector dependent mobility functions to create models with consistent dynamics across different scales.

Contribution

The paper presents a new dynamic coarse-graining scheme employing mobility functions and internal friction parameters to accurately map polymer dynamics at various scales.

Findings

Successfully maps Rouse polymers onto ultrashort CG chains with N=4.

Method maintains static structure while adjusting local dynamics.

Applicable to homopolymers and requires longer chains for copolymers.

Abstract

We propose a dynamic coarse-graining (CG) scheme for mapping heterogeneous polymer fluids onto extremely CG models in a dynamically consistent manner. The idea is to use as target function for the mapping a wave-vector dependent mobility function derived from the single-chain dynamic structure factor, which is calculated in the microscopic reference system. In previous work, we have shown that dynamic density functional calculations based on this mobility function can accurately reproduce the order/disorder kinetics in polymer melts, thus it is a suitable starting point for dynamic mapping. To enable the mapping over a range of relevant wave vectors, we propose to modify the CG dynamics by introducing internal friction parameters that slow down the CG monomer dynamics on local scales, without affecting the static equilibrium structure of the system. We illustrate and discuss the method using the example of infinitely long linear Rouse polymers mapped onto ultrashort CG chains. We show that our method can be used to construct dynamically consistent CG models for homopolymers with CG chain length N=4, whereas for copolymers, longer CG chain lengths are necessary