Ion-transport materials are essential components for a variety of applications including ion exchange membranes, fuel cells, and redox-flow batteries. Polymers bearing pendant ionic groups are viable options for these applications, as the polymer backbone provides mechanical integrity and the ionic groups provide paths for charge conduction. Both the backbone and ionic groups can be tuned toward optimized material properties, performance, and stability. These features have significantly impacted the development of alkaline anion exchanges membranes (AEMs). In alkaline fuel cells, AEMs serve as a solid cationic support for hydroxide transport from cathode to anode. Various polymer backbone and cation pairings have been investigated toward highly robust and conductive thin film membranes, but no benchmark AEM has yet been developed. Concerns to be addressed with these materials center around long-term mechanical integrity, stability, and hydroxide conductivity. Further understanding of how these aspects are influenced by backbone stiffness, cation identity, and polymer architecture would aid toward the fabrication of AEMs with improved mechanical and performance properties. Herein, we utilize ring opening metathesis polymerization (ROMP) to develop a series of AEMs derived from cylic olefin copolymers (COCs). Rigid cyclic substituents are incorporated statistically along the polymer backbone, leading to high <i>T<sub>g</sub> </i>(&gt;100 °C) ROMP polymers with good mechanical integrity and film forming properties. We employ the ubiquitous trimethylammonium cation as well as charge delocalized tetra(dialkylamino)phosphonium cation derivatives and compare the resulting polymer physical properties, performance properties, and alkaline stablity.

Cyclic olefin copolymer based anion exchange membranes

ACS Spring Meeting 2021

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