The Comparison of Ionic Aggregate Structure and Structural Morphology of Polyether‐Ester‐Sulfonate Copolymer Ionomers With Lithium and Sodium Counterions

ABSTRACT

Using all‐atom molecular dynamics simulations, this paper investigates the differences in ionic aggregate structure and structural morphology of polyether‐ester sulfonate copolymers (containing poly(ethylene oxide) (PEO) and poly(tetramethylene oxide) (PTMO)) with Li ⁺ and Na ⁺ as counterions. Compared with the 100% PEO‐Na ⁺ system, the solvation effect of ether oxygen atoms on cations in the PEO‐Li ⁺ system is weaker, and Coulombic interactions dominate. This results from the non‐metallic nature of Li ⁺ . The different solvation effects in both systems lead to distinct ionic aggregate states and structures, which are further analyzed and confirmed through the ionic interaction energy and the number/size of clusters in the systems. Additionally, the changes in ion aggregation structure and solvation effects result in distinct structural morphologies of the two copolymer systems, which are reflected in the varying degree of phase separation. The weaker phase separation in the Li ⁺ system arises from greater ion aggregation at the PEO/PTMO interface, which enhances the compatibility between the two microdomains. These findings about the interplay between the ionic aggregate structure and structural morphology are vital for the design and optimization of single‐ion conductor polyelectrolytes.