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陕西快乐十分中奖规则:Highly conductive and chemically stable alkaline anion exchange membranes via ROMP of trans-cyclooctene derivatives
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Alkaline exchange membrane fuel cells (AEMFCs) can generate electricity from chemical energy in renewable fuels (e.g., H2) using inexpensive nonplatinum electrode catalysts. The alkaline anion exchange membrane (AAEM) is a major component in AEMFCs, as its hydroxide conductivity and alkaline stability are directly related to the power density and durability of the AEMFC. In this work, we synthesized AAEMs consisting of polyethylene backbones and alkaline-stable imidazolium cations via the living ring-opening metathesis polymerization of trans-cyclooctene monomers, wherein either block or random copolymer sequences can be achieved. The polymer morphology was studied by transmission electron microscopy to understand the difference in conductivity. High hydroxide conductivities and alkaline stabilities were observed for the cross-linked random copolymer AAEMs.
Alkaline anion exchange membranes (AAEMs) are an important component of alkaline exchange membrane fuel cells (AEMFCs), which facilitate the efficient conversion of fuels to electricity using nonplatinum electrode catalysts. However, low hydroxide conductivity and poor long-term alkaline stability of AAEMs are the major limitations for the widespread application of AEMFCs. In this paper, we report the synthesis of highly conductive and chemically stable AAEMs from the living polymerization of trans-cyclooctenes. A trans-cyclooctene–fused imidazolium monomer was designed and synthesized on gram scale. Using these highly ring-strained monomers, we produced a range of block and random copolymers. Surprisingly, AAEMs made from the random copolymer exhibited much higher conductivities than their block copolymer analogs. Investigation by transmission electron microscopy showed that the block copolymers had a disordered microphase segregation which likely impeded ion conduction. A cross-linked random copolymer demonstrated a high level of hydroxide conductivity (134 mS/cm at 80 °C). More importantly, the membranes exhibited excellent chemical stability due to the incorporation of highly alkaline-stable multisubstituted imidazolium cations. No chemical degradation was detected by 1H NMR spectroscopy when the polymers were treated with 2 M KOH in CD3OH at 80 °C for 30 d.
- alkaline anion exchange membrane
- block and random copolymer
- cross-linked polymer
- transmission electron microscopy
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Author contributions: W.Y. and G.W.C. designed research; W.Y., E.P., and S.N.M. performed research; W.Y., E.P., S.N.M., D.A.M., and G.W.C. analyzed data; and W.Y., E.P., S.N.M., D.A.M., and G.W.C. wrote the paper.
Reviewers: J.S.M., University of Illinois at Urbana–Champaign; and T.M.S., Massachusetts Institute of Technology.
The authors declare no conflict of interest.
Data deposition: The atomic coordinates and structure factors have been deposited in the Cambridge Structural Database, Cambridge Crystallographic Data Centre, Cambridge CB2 1EZ, United Kingdom, www.ccdc.cam.ac.uk (CSD reference no. 1878813).
This article contains supporting information online at www.pnas.org/lookup/suppl/doi:10.1073/pnas.1900988116/-/DCSupplemental.
Published under the PNAS license.