Design and Synthesis of Imidazolium-Mediated Tröger's Base-Containing Ionene Polymers for Advanced CO Separation Membranes.

It is highly desirable to integrate the CO solubility benefits of ionic liquids (ILs) in polymeric membrane systems for effective CO separations. Herein, we are exclusively exploring a series of four novel imidazolium-mediated Tröger's base (TB)-containing ionene polymers for enhanced CO separation. The two diimidazole-functionalized Tröger's base monomers synthesized from "ortho"- and "para"-substituted imidazole anilines were polymerized with equimolar amounts of two different aromatic and aliphatic comonomers (α,α'-dichloro--xylene and 1,10-dibromodecane, respectively) via Menshutkin reactions to obtain four respective ionene polymers ([Im-TB(&)-Xy][Cl] and ([Im-TB(&)-C][Br], respectively). The resulting ionene polymers having halide anions were exchanged with [TfN] anions, yielding a novel Tröger's base material [Im-TB(x)-R][TfN] or "Im-TB-Ionenes". The structural and physical properties as well as the gas separation behaviors of the copolymers of aromatic and aliphatic Im-TB-Ionenes have been extensively investigated with respect to the regiochemistry of imidazolium groups at the ortho and para positions of the TB unit. The imidazolium-mediated TB-Ionenes showed high CO solubility and hence an excellent CO/CH permselectivity of 82.5. The Im-TB-Ionenes also displayed good thermal and mechanical stabilities.