Superionic Disulfonic Acid Polymers

Abstract Acid‐functionalized polymers have received significant attention for use in energy conversion systems. Sulfonated aromatic polymers have been widely studied for utilization in energy conversion systems; however, the occurrence of side reactions or uncertainties in the substitution has hindered progress in enhancing their properties. In this study, an approach is presented for developing superionic sulfonated polymers through the strategic design of disulfonic acid polymers with precisely arranged acid groups that allow fine‐tuned molecular interactions at the molecular level. Notably, the synthesized polystyrene 3,4‐disulfonic acid (PS di 34S), with sulfonic acid groups in close proximity to the meta and para positions of the styrene ring, exhibits lower charged states, significantly reduced acidity and hydrophobic characteristics due to intra‐monomer hydrogen bonding interactions. When the PS di 34S doped with ionic liquids, these interactions decouple ion relaxation from polymer relaxation, contrary to the strong trade‐off between ionic conductivity and mechanical strength observed in other sulfonic acid polystyrene counterparts. The PS di 34S electrolytes exhibit superionic conduction behavior, with a room temperature conductivity of 1.2 mS cm −1 and a shear modulus of 52 MPa (calculated Young's modulus of 156 MPa). Controlled polymerization routes for obtaining disulfonic acid polymers with excellent electrolyte properties offer significant promise for a wide range of electrochemical applications.