Intrinsically Porous Polymers for Anion Exchange Membranes

Anion exchange membranes (AEMs) are a material characterized by their immobile cationic moieties, allowing for selective diffusion of anions. AEMs have applications in many next-generation electrochemical engineering applications to aid in the energy transition, including electrolysis, fuel cells, and redox flow batteries. Unfortunately, many AEMs suffer from chemical durability towards hydroxide, poor ionic conductivity, and/or ionic selectivity. AEMs are a prominent field in academic research, but shortcomings in these critical properties limit their translation to industrial processes. In recent years, researchers have discovered a class of material known as polymers of intrinsic microporosity (PIMs), which possess nanoscale porosity due to the poor chain packing of rigid polymers in solid-state membranes. This porosity allows for improved ion separation and conduction. In this work, we are seeking to synthesize PIM-based AEMs with a nonpolar backbone, giving them a strong resistance against degradation from hydroxide. Thus far, we have successfully formed quaternary ammonium functionalized PIMs from alkyl bromines tethers from the polymer backbone. Further optimization must be done to increase the molecular weight of these polymers, allowing for membrane formation. As this work advances, we will study the structure-property relationships towards AEM applications to help form a set of design rules for these materials.