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.