(526b) Designing Sophisticated Imidazolium Ionenes: A Structurally and Functionally Tailorable Platform for High-Performance Engineering Applications

We have designed and developed a series of high-performance (HP) ionenes, or polymers which contain ionic groups along the main chain rather than as pendants. These materials combine functional features utilized in high-performance engineering polymers with structural and ionic elements associated with leading gas separation media. These functional features are spaced by incorporated ionic groups along the main chain, specifically imidazolium cations paired with fluorinated anions (OTf, Tf₂N, BETI, etc.). Our methods take advantage of established chemistries that impart great control over repeat unit structure, charge density, and regiochemistry. Through manipulation of substituent position and monomer end groups, we have expanded the opportunities for incorporating, spatially distributing, and alternating structural and functional segments within each monomeric building block, which increases the complexity and molecular weight of the repeat unit. Varied connectivity and sophisticated structural segments known for imparting free volume, such as iptycene, spirobisindane, and Tröger’s base moieties, have also been incorporated along the backbone. These ionenes are robust, exhibiting good thermal and mechanical properties, but extremely tailorable based on the modular design and versatile synthetic approaches which allow for innumerable potential derivatives. Thus, the thermophysical properties of these materials are highly tunable based on deliberate combination of assorted monomers and linkages. These polymeric materials exhibit self-assembly when filled with “free” imidazolium-based ionic liquids (IL), which contributes additional tunability as the IL serves as a non-covalent cross-link between the polymer chains. We are investigating the effects of adding functional, ionic small molecules into the polymeric matrix which alter intramolecular interactions and promote further structuring within the ionic framework. These HP-ionenes are thoroughly characterized in order to develop structure-property relationships between the polymer properties and the structural and functional features. Similarly, the ionene + IL composites are characterized, in order to gain a better understanding of the coordination between polymer chains and dispersed ionic additives. The performance of these novel ionenes and composites is tested in diverse applications including gas separation membranes, fibers, coatings, and 3D printing materials.