Triazole-to-Triazolium Conversion Switches Smectic-to-Columnar Ordering in PEO-Based Lithium-Ion Conducting Liquid Crystals

We report a molecular design strategy to control the liquid crystalline(LC) nanostructure of polymer-tethered ionic meterials and thereby enhance solid-state Li* transport. A 1,2,3-triazole derivative bearing an ionophilic poly(ethylene oxide) (PEO, M_n=350g mol^-1) chain and ionophobic 3,7-dimethyloctyl groups was synthesized via CUAAC coupling. Quaternization of the triazole ring followed by anion metathesis with LiTFSI afforded an ionic-liquid (IL)-type triazolium-TFSI salt. Li⁺-conducting samples (1-Li⁺ and 2-Li⁺) were prepared at a fixed [LiTFSI]/[EO] molar ratio of 0.3. Thermal and optical analyses revealed that 1formed a smectic A (SmA) mesophase, whereas only an isotropic liquid phase was observed in 2. Notably, while 1-Li⁺ retained an SmA organization, 2-Li⁺ exhibited a hexagonal columnar (Col_h) mesophase with well-defined feflections indexed to a 2D hexagonal lattice (a = 67.4 Å), consistent with fan-like POM textures. The high ionophilic volume fraction of 2-Li⁺(0.75), arising from the combined PEO/LiTFSI/triazolium domain, is proposed to favor a columnar assembly in which a continuous ion-conducting matrix surrounds ionophobic cylindrical cores; the triazolium group is positioned near the interface and locally wrapped by PEO through cation-ether interactions. Electrochemical impedance spectroscopy demonstrated that 2-Li⁺ consistently outperforms 1-Li⁺, delivering 2.57-fold higher conductivity at 30 °C and reaching 4.01 × 10-4 S cm^-1 without organic solvents. These results highlight how IL engineering and LC morphology control create continuous percolating pathways for efficient Li+ transport in solvent-free electrolytes.