Anionic Glycidyl Triazolyl Polymers: Oppositely Charged Analogs of Imidazolium-Based Cationic Glycidyl Triazolyl Polymers

Glycidyl triazolyl polymer (GTP)-based anionic poly-(ionic liquid)-s comprising the trifluoromethanesulfonimide (TFSI) anion pendant and the 1-ethyl-3-methylimidazolium (EMIM) countercation were synthesized through Cu-(I)-catalyzed azide-alkyne cycloaddition between a glycidyl azide polymer and anionic alkyne derivatives. These polymers were designed as oppositely charged analogs of the cationic GTPs reported previously. The anionic GTPs were characterized by NMR, IR, size-exclusion chromatography, differential scanning calorimetry, thermogravimetric analysis, and impedance measurements. The anionic GTPs reported herein exhibited a lower critical solution temperature (LCST) type phase separation in acetone. The anionic GTPs with a longer side-chain spacer exhibited a lower glass transition temperature (T-g) and higher ionic conductivity (1.7 x 10(-6) S cm(-1) at 25 degrees C under anhydrous conditions). It was confirmed that the anionic GTPs contain 0.8-0.9 wt % water even after the drying process. It is considered that the residual water contributes to improving the ionic conductivity. Compared to the cationic GTP with a similar side-chain spacer, the anionic GTP exhibited higher T-g and lower ionic conductivity. The analysis based on the electrode polarization model indicated that the lower ionic conductivity would originate from lower conducting ion concentration and mobility. From the conducting ion mobility versus T (g)/T plot, it was confirmed that the anionic GTP with the short alkyl chain spacer gave higher conducting ion mobility than that with the ethylene oxide spacer, which suggested that the electrostatic interaction with the ether oxygen atoms could slow down the diffusion of the EMIM cation. Stronger electrostatic interaction between the TFSI pendant and EMIM cation than that between the EMIM pendant and TFSI counterion is a cause of stronger polymer-polymer interaction.