Mussel-inspired strategy towards functionalized reduced graphene oxide-crosslinked polysulfone-based anion exchange membranes with enhanced properties

Abstract

Chemical crosslinking is regard as an effective method to balance the ionic conductivity and dimensional stability of anion exchange membranes (AEMs). In this work, a series of crosslinked AEM composite membranes based on polydopamine-functionalized reduced graphene oxide (PDArGO) were constructed from quaternized polysulfone (QPSU) with amino groups via mussel-inspired chemistry strategy. On the one hand, as the dopant, the hydrogen bonding interaction between PDArGO and a large number of amino groups on the side chains of QPSU can enhance the water uptake of the membranes and has a positive influence on the ionic conductivity of composite membranes. On the other hand, PDArGO also acts as the crosslinker, which can form a micro-crosslinked structure with the amino groups on the side chains of the polymer through the Michael addition/schiff base reactions. Under the combined influence of the above two factors, the crosslinked composite AEMs exhibited special delightful properties. In general, the crosslinking reaction will lead to the decrease of the ionic conductivity of the membranes, but as for the membranes prepared by us, the ionic conductivity had been improved to some extent. Especially, the QPSU-1.5%-PDArGO exhibited 57% improvement in the hydroxide conductivity than that of pure QPSU membrane and reached the highest value of 61 mS cm−1 at 80 °C. Besides, the crosslinked membranes also exhibited strong dimensional stability, good mechanical strength, comparable alkaline stability and improved methanol permeability.