ROMP-Derived Ionic Functional Poly(Oxanorbornene Imides): A Modular Route to Poly(Ionic Liquid)s

In this work, we report the synthesis of five poly(ionic liquid) (PIL) homopolymers and diblock copolymers derived from bromo-alkyl-functionalized oxanorbornene imide monomers via ring-opening metathesis polymerization (ROMP). Subsequent yielded polymers were quaternized with 1-methylimidazole or N-methylpiperidine to afford imidazolium- or piperidinium-based bromide salts, which were then converted to their bis(trifluoromethanesulfonyl)imide (TFSI–) forms through anion exchange with lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). This approach provided PILs bearing either methylimidazolium (MIm+) or methylpiperidinium (MPip+) cations paired with TFSI– counterions in good to excellent yields. The influence of polymer architecture and tethered ionic functionalities on thermal behavior and ionic conductivity was systematically examined. Among the PILs, the MIm+/TFSI–-based homopolymer exhibited the highest ionic conductivity (4.37 × 10–5 S/cm) coupled with a relatively low glass transition temperature (47 °C), underscoring the role of segmental dynamics in facilitating ion transport. Collectively, these ROMP-derived PILs combine excellent thermal stability with favorable ionic conductivities, highlighting their potential as solid polymer electrolytes (SPEs) for lithium battery applications.