Molecular Engineering in Benzobisazole-Linked Polymers: Unveiling the Linkage Effect on Proton Conductivity and...

Area of Science:

• Polymer Chemistry
• Materials Science
• Electrochemistry

Background:

• Benzobisazole-linked polymers are promising proton-exchange electrolytes.
• Structural rigidity and limited chain dynamics hinder their practical use.

Purpose of the Study:

• Investigate the effect of linkage motifs on polymer properties.
• Develop novel benzobisazole-based polymers with improved proton conductivity.

Main Methods:

• Synthesized three vinylene-bridged zwitterionic benzobisazole polymers via aldol polycondensation.
• Acid-doped polymers including benzobisoxazole (PA@v-ZLP-NO), benzobisthiazole (PA@v-ZLP-NS), and benzobisimidazole (PA@v-ZLP-NN).
• Evaluated thermal, morphological, and proton conductivity properties.

Main Results:

• PA@v-ZLP-NN exhibited superior proton conductivity (2.0 × 10^-2 S/cm at 80°C, 98% RH).
• PA@v-ZLP-NN's performance is attributed to NH groups facilitating hydrogen bonding, self-protonation, and acid-base interactions.
• Low activation energy (0.11-0.25 eV) supports Grotthuss-type proton transport.

Conclusions:

• The linkage motif significantly impacts proton conductivity in benzobisazole polymers.
• PA@v-ZLP-NN demonstrates potential as a superior proton-exchange electrolyte.
• The study overcomes limitations of structural rigidity and restricted chain dynamics.