Understanding Morphology and Ion Transport in Novel Poly (cyclooctene) Based Membranes Under Humidified Conditions

Abstract

Anion Exchange membranes have been gaining popularity for their applications in fuel cells, CO2electrolysers, redox flow batteries, etc. The main focus has been in the area of synthesizing new polymers for these applications and understanding their morphological and transport properties under humidified conditions of operations. The main aim is toward increasing the ion transport and minimizing degradation over time. Phase separated morphology is one of the pathways to create defined ionic pathways to increase ion conductivity of the AEMs. Here we report morphological study performed on a polycyclooctene based triblock copolymer AEM, for electrochemical applications. We have performed in situ SAXS under humidified conditions on these AEMs of importance to understand the swelling and morphological behavior. AEMs in this study show lamellar morphology with a d spacing of 39-41nm. We also studied the mechanical properties of these AEMs. Mechanical properties of these membranes are good under dry and low temperature, but above 60°C and hydration the AEMs become soft. Our initial results show that the AEM is stable under alkaline conditions of operation and offers reasonable hydroxide conductivity (70mS/cm @ 60°C) under humidified conditions. Conductivity of these AEMs increases by 4 fold when humidity is increased from 80% to 95%. Overall we report a functional AEM with reasonable properties for electrochemical applications. Acknowledgements: We would like to thank the Army Research Office for funding this Multidisciplinary University Research Initiative under contract #W911NF-10-1-0520 and the Colorado School of Mines NMR facility, funded by National Science Foundation under the grant CHE-0923537.