Ion-Conductive Vitrimers Based on Backbone-Type Triazolium Poly(ionic liquid)s: Counterion-Dependent Dynamics and Backbone Flexibility

To simultaneously achieve high ionic conductivity and recyclability, vitrimers were prepared using backbone-type triazolium poly(ionic liquid)s (TPILs) that integrate ionic transport with dynamic network rearrangement via trans-N-alkylation. TPIL elastomers bearing I⁻, BF₄⁻, PF₆⁻, and TFSI⁻ counteranions were synthesized from “clickable” ionic liquid monomers, and their glass transition temperature (Tg), ionic conductivity, and vitrimeric dynamics were compared. Only the I⁻-based network exhibited stress relaxation at 170 °C, indicating that nucleophilic anions are important for bond exchange. However, a trade-off was observed between ionic transport and dynamic network rearrangement. Furthermore, mixed-anion TPIL elastomers using I⁻+TFSI⁻ exhibited lower Tg and higher ionic conductivity than I⁻-based elastomer, while still maintaining vitrimer-like relaxation. The segmental relaxation was decoupled from Arrhenius-type bond-exchange dynamics. Ionic conduction was dominated by segmental motion, with minimal contribution from cross-link exchange. This design combining flexible polymer backbones and cooperative anion engineering can create recyclable, highly conductive polymer electrolytes.