Systematic coarse-graining of the dynamics of entangled polymer melts: the road from chemistry to rheology

Abstract

For optimal processing and design of entangled polymeric materials it is important to establish a rigorous link between the detailed molecular composition of the polymer and the viscoelastic properties of the macroscopic melt. We review current and past computer simulation techniques and critically assess their ability to provide such a link between chemistry and rheology. We distinguish between two classes of coarse-graining levels, which we term coarse-grained molecular dynamics (CGMD) and coarse-grained stochastic dynamics (CGSD). In CGMD the coarse-grained beads are still relatively hard, thus automatically preventing bond crossing. This also implies an upper limit on the number of atoms that can be lumped together (up to five backbone carbon atoms) and therefore on the longest chain lengths that can be studied. To reach a higher degree of coarse-graining, in CGSD many more atoms are lumped together (more than ten backbone carbon atoms), leading to relatively soft beads. In that case friction and stochastic forces dominate the interactions, and action must be undertaken to prevent bond crossing. We also review alternative methods that make use of the tube model of polymer dynamics, by obtaining the entanglement characteristics through a primitive path analysis and by simulation of a primitive chain network. We finally review super-coarse-grained methods in which an entire polymer is represented by a single particle, and comment on ways to include memory effects and transient forces.

Information-theoretic tools for parametrized coarse-graining of non-equilibrium extended systems

“…The proposed approach carries sufficient level of generality in order to be applicable to a wide class of stochastic processes, e.g., Langevin dynamics and KMC, without restriction to the dimension of the system, provided scalable efficient simulators are available to simulate the observables, (8) and (9). The proposed parametrized coarse-graining is applicable to any system for which a parametrized coarse-grained models are available, e.g., in coarse-graining of macromolecules and biomembranes, 30,32,38 . An obvious obstacle is that the path measure P [0,T ] is absolutely continuous with respect to Q [0,T ] , however, it does not significantly restrict the class of relevant applications as we typically deal with KMC or Markov Chain approximations resulting from a discretization of Molecular Dynamics with noise.…”

“…Typical examples include reaction-diffusion systems in heteroepitaxial catalytic materials, polymeric flows and separation processes in microporous materials, 32,35,36 . In this paper we develop reliable model-reduction methods, i.e., having controlled fidelity of approximation, and capable to handle extended, non-equilibrium statistical mechanics models.…”

Challenges in Multiscale Modeling of Polymer Dynamics

“…Multiscale modeling techniques will play an important role in this process of verifying new and existing models, but also in guiding theoretical development and exploring unexpected physical phenomena. There exist some excellent and recent reviews on the coarse-graining of entangled polymers, focusing on static properties [35][36][37], dynamic properties [38][39][40][41] and the comparison between different systematic coarse-graining methods [42,43]. There are also several books on multiscale modeling of polymers and biomolecules [35,[44][45][46][47][48], which cover particular methods not captured in this review.…”

Resolving Dynamic Properties of Polymers through Coarse-Grained Computational Studies

“…Bead diameter corresponds to the minimum in the nonbonded interaction for each CG model. grained while still appropriately capturing polymer properties and dynamics [5]. The current study probes the effects of the degree of coarse graining of polymers on their dynamic and static properties.…”