Scalability of Coarse‐Grained Potentials Generated from Iterative Boltzmann Inversion for Polymers: Case Study on Polycarbonates

Abstract

Using systematic coarse‐grained (CG) techniques such as iterative Boltzmann inversion (IBI) is an efficient means to simulate high molecular weight polymer melts within reasonable computational time. One drawback of such an approach is however the need to carry out extensive atomistic simulations in order to extrapolate the necessary distributions to derive the inter and intrabead force field parameters. Here it is shown that it is possible to use atomistic simulations of relative short oligomers to develop the CG model for high molecular weight polymers. In particular for the specific case of polycarbonates, it is found that the structural properties (end‐to‐end distance, radius of gyration and their distributions) are similar irrespective of whether the CG potentials are derived from 5‐mer or 10‐mer melt systems. Dynamical properties of the CG systems are smoother and faster than the atomistic ones. Scaling factor, derived by overlapping the CG mean square displacement curves (obtained from different CG IBI potentials) over the atomistic ones, also scales the autocorrelation functions. A prediction of the dynamical scaling factor in the case of the unavailability of atomistic simulations is also discussed. The dynamical properties of the CG melts are modeled reasonably well by all the CG potentials derived from atomistic simulations of short oligomers.

Energy renormalization for coarse-graining polymers having different segmental structures

“…Figure 1B shows a snapshot of the CG model of one PC chain with a chain length of N = 10 (i.e., number of monomers per chain) overlaid with the atomistic model. A similar mapping scheme for coarse-graining PC has also been adopted in previous works (20)(21)(22). The bonded interactions of the CG model, including bonds, angles, and dihedrals, were derived by matching their probability distributions of the AA model using the IBM.…”

“…Several previous studies on the development of the CG models of PC (developed via the IBM) have focused more on the static and structural properties, and those models typically exhibit a marked speedup in dynamics compared to its AA counterpart (20)(21)(22). In this study, we aim to develop a CG model using the ER method that can capture its temperature-dependent dynamic properties over a wide temperature range.…”

Understanding the Role of Cohesive Interaction in Mechanical Behavior of a Glassy Polymer

“…To address this issue, molecular dynamics (MD) simulations are often employed to provide valuable insights into the deformational responses and molecular mechanisms of glassy polymers. , In particular, coarse-grained (CG) MD simulations, where clusters of atoms in the all-atomistic (AA) structures are effectively grouped into CG “super-atoms” by integrating out nonessential atomistic features, allow for systematic investigation of fundamental molecular parameters while offering much improved computational efficiency to overcome spatiotemporal limitations. − To explore the mechanical behavior of glassy polymers, we take bisphenol-A polycarbonate (BPA-PC or PC) as a model system using CG-MD simulations because of its extensive usages in structural applications due to their notable mechanical properties, such as high impact resistance, strength, modulus of elasticity, and optical transparency . Previously, several computationally efficient CG models have been proposed to capture the key structural and dynamic features of the AA model of PC. − Using an iterative Boltzmann inversion (IBI) method, León et al have developed a CG model of PC to explore the effects of entanglement and molecular weight on polymer dynamics, yielding a reasonable agreement with experiments. Built upon earlier efforts, Palczynski et al proposed a modified CG potential where the far-field Taylor expansion of the Hamaker interaction was implemented to capture intermolecular interaction of polymer chains, leading to improved approximations of the glass-transition and mechanical properties of the CG model of PC in comparison with experimental data.…”

“…35 Previously, several computationally efficient CG models have been proposed to capture the key structural and dynamic features of the AA model of PC. 36−45 Using an iterative Boltzmann inversion (IBI) method, 38 Leoń et al 37 have developed a CG model of PC to explore the effects of entanglement and molecular weight on polymer dynamics, yielding a reasonable agreement with experiments. Built upon earlier efforts, Palczynski et al 39 proposed a modified CG potential where the far-field Taylor expansion of the Hamaker interaction was implemented to capture intermolecular interaction of polymer chains, leading to improved approximations of the glass-transition and mechanical properties of the CG model of PC in comparison with experimental data.…”

Coarse-Grained Molecular Dynamics Force-Field for Polyacrylamide in Infinite Dilution Derived from Iterative Boltzmann Inversion and MARTINI Force-Field

“…Yet another popular CG strategy is the Iterative Boltzmann Inversion (IBI) that targets the structural representation of the atomistic description. , IBI is a protocol of iterative optimization on the interaction potentials between coarse-grained sites so as to match the structural distributions (pair correlations) of the underlying atomistic model, such as the bond, angle, dihedral probability distributions, and the radial distribution functions (RDFs) between the CG sites. IBI is mostly used for homogeneous systems like polymer melts. ,− In this article, we introduce a novel idea of coarse-graining aqueous polyacrylamide by integrating the MARTINI framework with the IBI methodology to reproduce both the structure and thermodynamics of the basal atomistic system. This was achieved by the inclusion of MARTINI water beads in the CG system while optimizing potentials of the polymer–polymer interactions alone.…”