Systematic and simulation-free coarse graining of homopolymer melts: A structure-based study

Abstract

We propose a systematic and simulation-free strategy for coarse graining of homopolymer melts, where each chain of Nm monomers is uniformly divided into N segments, with the spatial position of each segment corresponding to the center-of-mass of its monomers. We use integral-equation theories suitable for the study of equilibrium properties of polymers, instead of many-chain molecular simulations, to obtain the structural and thermodynamic properties of both original and coarse-grained (CG) systems, and quantitatively examine how the effective pair potentials between CG segments and the thermodynamic properties of CG systems vary with N. Our systematic and simulation-free strategy is much faster than those using many-chain simulations, thus effectively solving the transferability problem in coarse graining, and provides the quantitative basis for choosing the appropriate N-values. It also avoids the problems caused by finite-size effects and statistical uncertainties in many-chain simulations. Taking the simple hard-core Gaussian thread model [K. S. Schweizer and J. G. Curro, Chem. Phys. 149, 105 (1990)] as the original system, we demonstrate our strategy applied to structure-based coarse graining, which is quite general and versatile, and compare in detail the various integral-equation theories and closures for coarse graining. Our numerical results show that the effective CG potentials for various N and closures can be collapsed approximately onto the same curve, and that structure-based coarse graining cannot give thermodynamic consistency between original and CG systems at any N< Nm.

Systematic and simulation-free coarse graining of homopolymer melts: a relative-entropy-based study

“…In Ref. 12 The widely used st-based coarse graining matches the segment radial distribution functions between original and CG systems. Our systematic and simulation-free strategy is much faster than those using many-chain simulations, thus effectively solving the transferability problem in coarse graining, 16 and provides the quantitative basis for choosing the appropriate coarse-graining level.…”

“…Our systematic and simulation-free strategy is much faster than those using many-chain simulations, thus effectively solving the transferability problem in coarse graining, 16 and provides the quantitative basis for choosing the appropriate coarse-graining level. 12,17 In this work, we apply our systematic and simulation-free strategy to the recently proposed relative-entropy-based (RE-based) coarse graining, 9,18,19 which minimizes the information loss quantified by RE. 12 The widely used st-based coarse graining matches the segment radial distribution functions between original and CG systems.…”

Multiresolution Modeling of Semidilute Polymer Solutions: Coarse-Graining Using Wavelet-Accelerated Monte Carlo

“…This represents the good solvent regime, which was determined by calculating the theta point, which lies around /k B T ≈ −0.25. We simulate freely-jointed chains of length N = 2 5 = 32 to N = 2 13 Using these scaling relations, we determine the size of the chains of length N = 2 14 and 2 15 . The second set of simulations is performed on the coarse-grained model of a freely-jointed chain at three different values of /k B T under two levels of coarse-graining: N e = 32 and 64, where N e represents the size of the CG bead or number of monomers coarse-grained.…”

“…Lyubarstev et al [11] formulated a hierarchical multiscale approach that covered three different levels of description by using inverse Monte Carlo (IMC). Yang et al [12,13] developed structureand relative-entropy-based coarse-graining methods for homopolymer melts and compared the structural and thermodynamic properties of the original and the coarse-grained (CG) systems at various coarse-graining levels. Zhang et al [14] developed an elegant hierarchical coarse-graining and reverse-mapping strategy to model high molecular weight polymer melts, mapping the atomistic chains onto a model of soft spheres with fluctuating size.…”

Communication: One size fits all: Equilibrating chemically different polymer liquids through universal long-wavelength description

“…Nevertheless, fine-graining is feasible 22 considering the blobs as soft spheres 23 with simple interactions parameterized from the reference microscopic simulations. Alternatively, somewhat more complex chemistry-specific blob-based models can be developed from integral equation theories, 8,24,25 reducing in the future the need for such calibration data. Once the blobs become sufficiently small, microscopic details can be introduced.…”