Exo-selective, Reductive Heck Derived Polynorbornenes with Enhanced Molecular Weights, Yields, and Hydrocarbon Gas Transport Properties

• Published in: ACS macro letters 2020-09, Vol.9 (9), p.1363-1368
• Main Authors: Sundell, Benjamin J, Lawrence, John A, Harrigan, Daniel J, Lin, Sibo, Headrick, Tatiana P, O’Brien, Jeremy T, Penniman, William F, Sandler, Nathan
• Format: Article
• Language: English
• ISSN: 2161-1653; 2161-1653
• DOI: 10.1021/acsmacrolett.0c00555

Next-generation membranes use highly engineered polymeric structures with enhanced chain rigidity, yet difficulties in polymerization often limit molecular weights required for film formation. Addition-type polynorbornenes are promising materials for industrial gas separations, but suffer from these limitations owing to endo−exo monomeric mixtures that restrict polymerization sites. In this work, a synthetic approach employing the reductive Mizoroki–Heck reaction resulted in exo-selective products that polymerized up to >99% yields for ROMP and addition-type polymers, achieving molecular weights an order of magnitude higher than addition-type polymers from endo−exo mixtures and impressive side group stereoregularity. Due to this increased macromolecular control, these polynorbornenes demonstrate unique solubility-selective permeation with mixed gas selectivities that exceed commercially used PDMS. In addition to thermal and structural characterization, XRD and computational studies confirmed the results of pure and mixed-gas transport testing, which show highly rigid membranes with favorably disrupted chain packing.