Highly Alkaline Stable Crosslinked Piperidine-Functionalized Polynorbornene Anion Exchange Membranes

Abstract

The balance between long-term stability, size stability, and ion conductivity of anion exchange membranes (AEMs) under alkaline conditions is a key issue in their development. This article improves the alkaline stability of the membrane by selecting main chains and functional groups with good alkaline stability and using block and crosslinking methods. A series of anion exchange membranes with different crosslinking degrees, aPNB-O-DiPD-x, were prepared using a pyridine group with excellent alkali resistance as the cationic group and 1,3-di-4-pyridinylpropane (DiPD) as the crosslinking agent. Compared to uncrosslinked membranes, crosslinked membranes significantly increase their tensile strength and successfully suppress the swelling phenomenon caused by excessive water absorption. AFM and SAXS tests show that the crosslinked membrane has a clear phase separation structure. The ion conductivity of the crosslinked membrane aPNB-O-DiPD-5 at 80°C is 88.85 mS cm⁻¹, and it still retains 85.8% ion conductivity after soaking in 1 M sodium hydroxide solution for 840 h. In summary, the presence of crosslinking network in the micro crosslinked membrane aPNB-O-DiPD-x not only suppresses excessive water absorption but also improves the size stability of the membrane. At the same time, it has good ion conductivity and alkali stability, which has certain potential in fuel cells.