Solvation Energy of Ions in Polymers: Effects of Chain Length and Connectivity on Saturated Dipoles near Ions

Abstract

We illustrate the effects of chain connectivity on the solvation energy of ions immersed in polymer liquids by developing a new coarse-grained molecular dynamics simulation. Our theory accounts for the dielectric response of the polymers through the connection of dipolar, monomeric units with nonlinear springs. In stark contrast to the standard Born solvation energy of ions, our results depend substantially on the chain length of the polymers. We also demonstrate the marked difference in the solvation energies of the ions immersed in non-polymeric particle mixtures, single-component polymers, polymer blends, and block copolymers. Thus, we suggest that the chain architecture of polymers is a key factor in ion solvation, whereas this feature is often inadequately considered in main theory and simulation literature. Our results are consistent with those predicted by previous coarse-grained mean-field theories when the dipole moment of the polymer compositions is relatively small. However, we also demonstrate that the strong ion-dipole and dipole-dipole interactions cause the chain-like association of the monomeric units, resulting in a qualitative discrepancy between the mean-field theory and simulation. Such a strong electrostatic correlation may reverse the dependence of the chain length on the solvation energy of the ions in the polymers.

Solvation Energy of Ions in a Stockmayer Fluid

“…This work was originally based on simulations constructed by Lijun Liu, a former member of Dr. Nakamura's research group [29]. Lijun created his own Molecular Dynamics program whereas for this work LAMMPS was used.…”

Multivalent ion conduction in solid polymer systems

“…The connectivity and chain architecture of polymers has been shown to affect the local dielectric environment around solvated ions, leading to further behavioral differences between polymers and liquid electrolytes. [15][16] The use of more polarizable or larger counterions with smaller lattice energies should lead to higher dissociation rates and improved ionic conductivity. 17 Further, while increasing salt concentration should increase ion concentration, ion-ion interactions result in the formation of ion pairs or larger aggregates which reduce the ion concentration from its theoretical maximum value.…”

Transport Mechanisms Underlying Ionic Conductivity in Nanoparticle-Based Single-Ion Electrolytes

“…3 In lithium-salt doped polymer electrolytes, the addition of nanoparticles has been reported to increase t Li + . 3,[6][7][8][9][10][11][12][13] Single-ion conduction (t Li + ≈ 1) was recently observed for nanoparticle-based lithium salts in polymeric matrices 14 and oligomeric solvents. 15,16 In the latter systems, anion immobilization was achieved by grafting the anionic species onto the surface of nanoparticles.…”

“…While the mechanisms underlying ion transport in lithium-salt doped nanocomposite electrolytes have been examined, 8,[11][12][13] those governing ion transport in the newer class of nanoparticle-based single-ion conducting electrolytes remain poorly understood. Notably, the origins of an optimal nanoparticle loading for (maximizing) ionic conductivity and the pronounced influence that modifying the nanoparticle-tethered counterions has on the magni-tude of the conductivity 15 are still unresolved.…”