(519d) A Versatile Microporous Poly(Arylene Ether) Platform for Membrane-Based Gas Separation

Membrane-based gas separations exhibit several advantages over conventional separation methods such as cryogenic distillation and adsorption technologies due to the absence of energy-intensive phase changes as well as the lack of toxic chemicals. However, it remains a challenge to synthesize materials suitable for membrane separations which demands high material processability and high gas separation performance. Microporous organic polymers (MOPs) is a class of materials that combine the gas sieving capability of microporous materials with the solution-processability of organic polymers. For this project, we present the rational design and synthesis of linear microporous poly(arylene ether)s (PAEs) via Pd-catalyzed C-O polymerization reactions. The scaffold of these new microporous polymers consists of rigid three-dimensional triptycene and highly stereocontorted spirobifluorene, generating a large internal free volume within the polymer matrix. This robust methodology for the PAEs synthesis allows for the facile incorporation of functionalities and branched linkers to enhance the membrane’s permeation and mechanical properties, while remaining solution-processable for membrane fabrication. Such properties are rare in classic polymers of intrinsic microporosity (PIMs). Better CO₂ separation is also achieved by incorporating CO₂-philic groups, such as nitrile and tertiary amine groups, into this microporous polymeric scaffold. Furthermore, a branched polymer prepared using this synthetic strategy showed good gas separation performance and enhanced mechanical properties, which allowed for the formation of a submicron defect-free film with permeance-selectivity property sets that are comparable to high-performance ultrathin polymer membranes that have been optimized at industrial scale. The easily accessible PAE branching motif also endows these materials with plasticization resistance which enhances the longevity of the membrane, addressing a challenge facing many commercially available polymeric membranes. Results for the outstanding mechanical properties and gas transport performances will be presented for several gas separations of interest. The high physical stability, structural flexibility and and ease-of-processing suggest that this new platform of microporous polymers provide generalizable design strategies to address outstanding separation challenges for gas separation membranes. The methodology, implications, and future directions of applying this new class of PAEs to membrane-based gas separations will be outlined in this presentation.