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.