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 and 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. We overcome this trade-off by mixing anions. Mixed-anion TPIL elastomers using I– and TFSI– exhibited lower Tg and higher ionic conductivity than I–-based elastomer, while still maintaining vitrimer-like relaxation. Rheological analysis revealed a decoupling between segment relaxation and bond exchange dynamics in vitrimer-like elastomers. The design combining flexible polymer backbones and mixed-anion engineering can create recyclable, highly conductive polymer electrolyte networks.