Molecular Dynamics Simulations of Ion-Containing Polymers Using Generic Coarse-Grained Models

KH Shen and MD Fan and LM Hall, MACROMOLECULES, 54, 2031-2052 (2021).

DOI: 10.1021/acs.macromol.0c02557

Molecular dynamics simulations with generic bead-spring models have been instrumental in revealing the molecular-scale behavior that underlies structure-property relationships of various types of polymeric systems. The generic, coarse-grained modeling approach does not include atomistic detail and is not focused on quantitatively matching the properties of a particular chemical system, though typically several parameters are included that can be tuned to consider different types of chemistries. Besides allowing access to longer length and time scales due to computational efficiency, this type of approach is advantageous in that the physical insight gained is often relevant across the entire class of related materials. The connectivity and number of beads in a generic bead-spring models can be adjusted in an obvious manner to describe the most basic homopolymer features (e.g., to consider different chain lengths and linear versus branched architectures). In uncharged copolymers or solvent-containing systems, the chemical interactions between components are considered by adjusting the strength of the various pairwise interparticle potentials (usually without changing their form). However, ions can have stronger and longer-ranged interactions with each other, with solvents, and with monomers that can require additional complexity be added to appropriately describe relevant phenomena in ion-containing polymeric systems. Recent efforts are pushing the boundaries of the generic coarse-grained approach by including additional ion-ion or ion-polymer interactions to more closely capture and analyze such phenomena, while still avoiding detailed and specific empirical adjustments that would make the model only apply to a single chemical system. In this perspective, we highlight a variety of recent molecular dynamics work that applies generic coarse-grained models to study ion-containing polymeric materials. We also discuss possible future directions and challenges of the generic coarse-graining approach in this area.

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