Ab-initio Coarse-Graining of Entangled Polymer Systems

Multiscale Modeling and Coarse Graining of Polymer Dynamics: Simulations Guided by Statistical Beyond-Equilibrium Thermodynamics

“…Dissipation and friction are more properly accounted for in [58,136,138,139,172]. These authors, however, arrive at a daunting assessment: "We therefore conclude that coarse-grained models lack thermodynamic consistency" [138].…”

“…in [51,54,55]. From such detailed atomistic molecular dynamics (MD) simulations, the linear viscoelastic properties can be computed by Green-Kubo relationships [56,57,58]. Also less detailed bead-spring models are available; a prototypical model is that of Kremer and Grest [59] (or variants thereof [60]), which neglects chemical details and instead focuses on the interplay between chain connectivity and excluded volume effects.…”

“…Here, we aim to shortly review some recent coarse-graining and multi-scale methods (see [23,58,79,91,92,93,94,95] and also [96,97,98,99] for recent reviews of such methods for polymers and in a more general context, respectively), but also to put forward some new ideas for addressing such issues, which could eventually allow to model the macroscale quantities of interest by a suitable coarse-graining procedure. We will see that, if one is guided by nonequilibrium statistical mechanics and thermodynamics, it is possible to design well-founded multi-scale modeling tools that can link microscopic models with macroscopic constitutive equations.…”

“…Such multi-scale modeling tools benefit from recently proposed approaches for static coarse graining which are mainly built on potentials of mean force [79,100,101]. For dynamical properties, however, coarse-grained models need to account for dissipative effects that arise due to fast degrees of freedom that are eliminated (for example via projection operators) in favor of the remaining slowly varying ones [56,58,102,103]. In a flow situation, these slow dynamical variables depart from their values in the quiescent fluid, while all other (faster) degrees of freedom track the evolution of the structural parameters; i.e., they are assumed to be in local equilibrium subject to the constraints imposed by the values of the structural parameters at all times.…”

“…in [123,135]. For some notable exceptions see [58]. Considerable work is definitely needed in order to arrive at a thermodynamically consistent description of a model system at the two levels of analysis (atomistic and coarse-grained), which will eliminate all these undesired symptoms and errors.…”