Comparison Between Coarse‐Graining Models for Polymer Systems: Two Mapping Schemes for Polystyrene

Abstract

We present a detailed study of a new, optimized coarse‐grained (CG) model of polystyrene (PS) and compare it with a recently published one (Harmandaris et al., Macromolecules 2006, 39, 6708). By implementing a different mapping scheme, the new model, augmented with softer nonbonded interactions, better reproduces the local chain conformations and melt packing observed in atomistic simulations of atactic PS. Both models properly predict the bonded distributions and are capable of simulating different tacticities without needing sidegroups. Both CG models fit dynamic data from long atomistic simulations after determining the scale factor for the simulation time. Together with a rigorous back‐mapping procedure from the mesoscopic to atomistic description, this opens up a very feasible way for generating very long atomistic trajectories.magnified image

Molecular dynamics of polyisoprene/polystyrene oligomer blends: The role of self-concentration and fluctuations on blend dynamics

“…34 The chain dimensions as well as the structure of PS bulk systems are in good agreement with available experimental data. 35,36 It is important to note that this model predicts slower PS dynamics (a factor of about 4-5), compared to experimental data from dielectric spectroscopy. 37 For PS the extracted value for the characteristic ratio is about 5.0, lower than the high molecular value of about 9.8 as reported in previous studies.…”

Challenges in Multiscale Modeling of Polymer Dynamics

“…Correlation uniformity is a basic criterion highlighting the proper choice of the super atom in coarse-graining, as it relates to whether the factorization assumption of the probability distributions is valid. Such a criterion has been checked in detail for different coarse-graining models, through combined p R (θ) versus p R (φ) distribution plots (see Figure 3 in [188]). It is also more convenient to represent a group of atoms as a spherical super atom with an isotropic potential, instead of an ellipsoidal super atom with anisotropic potential.…”

“…Qian et al [69] chose another mapping scheme (see Figure 11c). The newly obtained potentials can reproduce the isothermal compressibility and structure properties of the PS melts from 400 K to 500 K. Kremer and his co-workers used yet another mapping scheme, as shown in Figure 11d [188,201]. They split the PS monomer into two parts, and each of them was represented by one super atom, which is a so-called "2:1" coarse-grained model.…”

“…They split the PS monomer into two parts, and each of them was represented by one super atom, which is a so-called "2:1" coarse-grained model. The derived model can represent the PS sequence with varying tacticities and has been validated for the structural and dynamic properties of atactic PS [188,201]. These models have recently been used to distinguish the dynamics of iso-, syndio-and atactic PS polymers.…”

“…From these studies, it is important to know that although there are different ways to define the super atom in deriving a coarse-grained model, the static, dynamic or thermodynamic properties of the coarse-grained model should be tested and validated before it is further applied [42]. [195][196][197]; (b) [185,200]; (c) [69]; and (d) [188,201]. Superatom Center…”