Rubbery Ionogels and Glassy lonogels: Design and Ion Conduction

Ionic-liquid based gels were prepared by employing elastomer or silicate network as the host polymer. Ionic liquids having bis (trifluoromethansulfonyl)imide anions (Tf2N-) are compatible to nitrile-butadiene rubber. The simple gel composed of rubber and ionic liquid gradually lost its elasticity with an increase of ionic liquid content, however. The elasticity was found to be improved by adding lithium salts (LiTf2N or LiBF4) into the gel. The resulting rubbery gel showed high ionic conductivity above 10(-4) S cm(-1) at room temperature. The lithium ion transfer number was improved further by employing zwitterions. On the other hand, a glass-like gel was obtained by sol-gel processing. A Bronsted acidic ionic liquid was employed to induce proton conductivity to the gel in this case. Because of the high thermal stability of both the inorganic polymer and the ionic liquid, the gel showed stable proton conductivity over a wide temperature range. In-situ sol-gel processing was performed to obtain a novel composite based on a polymerized ionic liquid and a silica-derived network.