(348h) Fine-Tuning of Ionene Backbones with High-Free-Volume Elements for High-Performance CO2 Separation Membranes

The development and commercialization of CO₂ sequestration or capture methods have become an important part of many industries as well as laboratory applications such as foam blowing, the production of urea, fertilizers, dry ice, and food/beverages, and in the supercritical state as a supercritical solvent and enhanced oil recovery (EOR) as a miscible gas to reduce the interfacial tension between oil and water. We investigate the use of CO₂ solubilizing ionic liquids in polymeric membrane systems for high degrees of membrane tunability and effect/control over polymer nanostructure with enhanced CO₂ separation properties. We have focused on the design and synthesis of various imidazole functionalized monomers having kinked or bridged bicyclic linking groups with a site of contortion that can rigidify polymer chain and generate imidazolium-ionenes with microporosity in the polymer matrix, which anticipated to share similar characteristics of polymers of intrinsic microporosity (PIMs). Spirobisindane, Tröger's base, and benzoxazole monomers having diimidazole functionalities were newly developed to synthesize various Ionene-PIMs. We also successfully developed V-shaped sulfonimide monomers for the synthesis of corresponding anionic forms of the ionenes which are unprecedented in the literature and will open-up broad new possibilities in polymer design with applications far beyond just gas separation membranes. Overall, the membranes prepared from these newly developed high free volume ionene polymers displayed extraordinary CO₂ separation properties, together with excellent mechanical and thermal stabilities. This presentation will detail our "bottom-up" approach of new ionene polymer architectures which contain the high free volume elements (e.g., Spirobisindane, Tröger's Base, Benzoxazole, Sulfonimides, etc.) covalently bonded to ionic groups and associated with extraordinary CO₂ separation over other light gases such as H₂, N₂, and CH₄.