Chemically Folded Polyelectrolytes with Superior Alkaline Stability

Abstract

In recent years, the development of anion-exchange membranes (AEMs) for anion-exchange membrane fuel cell (AEMFC) applications has been rapidly growing due to their numerous advantages over mainstream proton-exchange membrane fuel cells. However, a major challenge in the development of practical AEMs is the low chemical stability of the AEM quaternary ammonium (QA) functional groups in the strongly alkaline and the relatively dry environment produced during operation of the AEMFC. Herein, we investigate the effect of polymer chain folding on the chemical stability of the QA groups. While these polymers have virtually the same chemical composition, their molecular architectures are quite different, significantly affecting the kinetics of nucleophilic attacks on the QAs embedded inside the folded chains. The stability tests reveal a remarkable improvement in the stability of the folded chains compared to the linear (unfolded) control, resulting in polyelectrolytes that are two orders of magnitude more stable. We provide here a simple method for the preparation of chemically stable AEMs with different QA groups and polymer backbones. These folded architectures present a very promising family of polyelectrolyte membranes for AEMFCs and other electrochemical applications.