(34a) Ionic Correlations in Polymer Nanostructures: From Block Copolymers to End-Charged Blends

Ionic interactions provide a powerful and tunable means to direct polymer phase behavior, with applications in solid-state batteries and polymer compatibilization. This talk explores two key systems—neutral-charged block copolymers and ion-functionalized polymer blends—using an electrostatic fluctuation-augmented self-consistent field theory. For AB block copolymers with partially charged A-blocks, we demonstrate that ion correlations induce a "chimney-like" phase diagram, but dielectric contrast between blocks weakens the "chimney-like" feature. As the A-block charge fraction increases, counterions shift from interfacial accumulation to more uniform distribution within the A-domain. Notably, smaller counterions promote localized ion distributions, leading to hierarchical nanostructures (e.g., alternating layers, concentric cylindrical shells, and spherical shells) in lamellar, cylindrical, and spherical phases, respectively. Application of our theory to the experimental data from Balsara and coworkers for poly(ethylene oxide)-block-polystyrene (PEO-b-PS) blended with LiTFSI show good agreement across a broad range compositions and interaction parameters.

In the second part, we examine polymer blends where each chain is end-functionalized with a single oppositely charged group. Strong ion correlations effectively link the polymers, inducing phase behavior resembling that of neutral block copolymers. However, the order-disorder transition occurs at a significantly lower critical χN than in neutral systems. Additionally, ion localization persists even in fully miscible blends, and we discuss the transition from macro- to microphase separation. These findings highlight the critical role of ionic interactions in tailoring polymer self-assembly for advanced materials.