Aging resistant, fluorinated aromatic polymers with ladderized, rigid kink-structured backbones for gas separations

A facile, robust and scalable one-pot synthesis of easily processable, film-forming, shape persistent polymers became a great challenge in membrane separation technologies. Herein, we report for the first time a simple methodology of engineering off main chain ether-bond-free, ladderized, fluorinated aromatic polymers with rigid kink-structured backbones by polymerization of planar dibenzofuran (DBF) possessing multiple competitive reactive sites with carbonyl compounds. Five polymers incorporating rigid planar dibenzofuran isomer moieties with different bulky pendant trifluoromethyl- and aryl fragments were synthesized by one-pot, room temperature, non-stoichiometric superacid catalyzed step-growth polymerization. These solution processable aromatic polymers with ladderized, rigid kink-structured backbones provided membranes with tunable gas separations, physical aging resistance, and good mechanical and thermal properties. The membranes displayed CO 2 permeability between 203 and 401 Barrer and H 2 permeability between 210 and 472 Barrer, with CO 2 /CH 4 and H 2 /CH 4 selectivity close to 2008 Robeson's upper bound. Their gas permeability is due to a high FFV caused by packing of their kink-structured backbones, bulky pendant groups and to a strong interaction between CO 2 and the ring fused oxygen atoms in the polymeric structure. Physical aging, measured in 30–40 μm films after 500 days, resulted in permeability drops from 17% to 39% with improved selectivity. The results obtained also demonstrate the versatility of this synthetic strategy based on superacid catalyzed polymerization to fabricate well-defined macromolecules with designed shape-persistent architecture for advanced membrane applications. • New aromatic fluoropolymers with ladderized, rigid, kink-structured backbones. • High performance functional polymers based on monomers with multiple reactive sites. • Rigid DBF isomer kink-structured fragments increase permeability and selectivity. • Combination of dibenzofuran moiety bulky fragments produced high FFV polymers. • Rigid kink-structured backbones of DBF poymers show aging resistant after 500 days.