Ion-containing polymers can be challenging to model due to their strong ion-ion and ion-polymer interactions as well as important features on disparate length and time scales arising from ion, segmental, and overall chain behavior. We have studied several types of ion-containing systems, starting from a generic Kremer-Grest type of model that captures monomer packing and noncrossability of chains, and adding long-ranged Coulomb interactions between ions scaled by a background dielectric constant. Depending on the system, further features such as adjusted monomer-monomer interactions to account for chemical differences in copolymers, adjusted monomer and ion sizes, and special ion-monomer potentials to account for ion solvation can be added. Copolymeric systems are especially complex as they may have microphase separated regions with significantly different dielectric strengths and degrees of ion solvation. In prior work, we used a uniform background dielectric strength, set to the average dielectric strength for mixed systems or set to the higher dielectric medium for strongly microphase separated systems in which the ions exist in the higher dielectric microphase. Along with strong selective ion-monomer interactions, this can yield the appropriate trends in structural properties and ion diffusion with ion concentration and molecular weight; a few examples will be highlighted here. Recent work in which we instead applied Drude oscillators to monomer beads to account for both ion solvation and dielectric strength effects at the same time and in a greater level of detail will also be discussed.

Structure and dynamics of ion-containing copolymers via generic coarse-grained molecular dynamics simulations

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