Chemically specific coarse-grain force-field with a dissipative potential: Preserving the structure, dynamics, and material properties of polymer melts

L. Johnson
National Institute of Standards and Technology,
United States

Keywords: polymer dynamics


Polymer dynamics are set by a hierarchy of length scales, making it computationally expensive to model polymeric systems both with the detail of an all-atom (AA) molecular simulation and to sufficiently long times in simulation. Coarse-grained (CG) models lump atoms into fewer CG sites while trying to retain some characteristic features of the AA representation, improve computational cost, and enable simulation of larger systems and/or to longer times. Here, we study a CG simulation model that aims to preserve both chemical specificity (typical of systematic CG methods) and dynamics (typical of phenomenological CG models) of a polymer melt. The model is parameterized in two steps. First, we generate the conservative part of the force-field using the iterative Boltzmann inversion (IBI) method to preserve the chemical specificity of the AA structure. Second, we recover the dynamics by introducing a Langevin thermostat, and thus a tunable friction coefficient, that we parameterize to correct for the sped-up dynamics of the IBI-generated force-field. We recently showed that we can recover AA dynamics by parameterizing the friction coefficient of the CG representation and compared the parameterization across various measures of translational and rotational motion [J. Chem. Phys. 154, 084114 (2021)]. Here, we test the parameterization of the dynamics compared to those targeted to recover a material property, the zero-shear viscosity. We show that the viscosity-based friction is consistent with the other measures and that viscosity may be more simply predicted by using the dynamics-based friction measures.