Molecular Engineering in Benzobisazole‐Linked Polymers: Unveiling the Linkage Effect on Proton Conductivity and Transport Pathways

ABSTRACT Benzobisazole‐linked polymers hold potential as proton‐exchange electrolytes; however, their structural rigidity and restricted chain dynamics limit their practical applications. This study investigates the linkage motif effect in three acid‐doped, vinylene‐bridged zwitterionic benzobisazole‐based polymers: benzobisoxazole (PA@v‐ZLP‐NO), benzobisthiazole (PA@v‐ZLP‐NS), and benzobisimidazole (PA@v‐ZLP‐NN), synthesized via aldol polycondensation, which exhibit distinct thermal and morphological properties to overcome this limitation. Interestingly, although PA@v‐ZLP‐NN is less electron‐deficient than PA@v‐ZLP‐NO and PA@v‐ZLP‐NS, it shows superior proton conductivity of 2.0 × 10 −2 S/cm at 80°C and 98% relative humidity, which is about 1.3 times higher than PA@v‐ZLP‐NS and 5.1 times higher than PA@v‐ZLP‐NO under identical conditions. The improved performance of PA@v‐ZLP‐NN stems from the presence of NH groups, which enable additional sites for hydrogen bonding in synergy with SO 3 − ions, self‐protonation, and dynamic proton transfer via acid–base interactions, thereby forming efficient proton‐transfer pathways. Their low activation energy (0.11–0.25 eV) supports Grotthuss‐type proton transport, highlighting their potential as superior proton‐exchange electrolytes.