We have designed and developed a library of high-performance (HP) ionenes, or polymers which contain ionic groups along the main chain rather than as pendants. These materials merge functionality utilized in high-performance engineering polymers, structural features associated with leading gas separation media, and precisely spaced ionic segments. These ionenes incorporate imidazolium cations paired with delocalized molecular anions (i.e. Tf<sub>2</sub>N), which are produced from established synthetic methods that impart great control over repeat unit complexity, functional group sequence, charge density, and regiochemistry. Through methodical variation of substituents, connectivity along the backbone, and the sequence of functional and ionic segments, we have expanded the opportunities for incorporating, distributing, and alternating structural features. These ionenes possess excellent thermal and mechanical properties, while the structural tailorability provides access to an array of interesting behaviors and architectures. These polymeric materials exhibit self-assembly and local structuring when impregnated with “free” imidazolium-based ionic liquids (IL) or functional ionic fillers, which contributes additional tunability and alters intramolecular interactions in the ionene matrix. These HP-ionenes and IL composites are thoroughly characterized to develop structure-property relationships and to elucidate the coordination between the dispersed, discrete additives and the polymeric ionene matrix. The applicability of these ionenes-IL composite systems is demonstrated by analyzing their performance as gas separation membranes, fibers, and 3D printing materials.

Molecular design of high performance ionenes and ionic liquid composites

ACS Fall 2021

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