Facile construction of crosslinked anion exchange membranes based on fluorenyl-containing polysulfone via click chemistry

Abstract

A series of fluorenyl-containing polysulfone-based crosslinked anion exchange membranes with high conductivity and excellent stability were fabricated via click chemistry. Azide groups were firstly introduced into the side chains of fluorenyl-containing polysulfone via the quaternization reaction, and then the designed bifunctional crosslinking agents containing alkyne groups with different lengths and polarities (hydrophilicity) were used to construct the crosslinked structure via the click reaction between azides and alkynes. The degree of crosslinking of membranes can be adjusted by controlling the content of the crosslinking agent. The proper crosslinking of AEMs in this work can tighten the internal packing structure of membranes, which could not only enhance the mechanical strength of AEMs but also improve the fuel permeability, alkaline resistance and oxidative stability of membranes. The water uptake and swelling ratio of the crosslinked AEMs were also improved with the increase of polarity and length of crosslinking agents. The hydroxide conductivity of d-CPFSU-1 was not decreased by crosslinking rather it increased to 193.95 mS cm⁻¹ at 80 °C due to the formation of a uniform nano-micro phase separation structure. Our study showed that AEMs with enhanced performance can be achieved by the design of crosslinking within the control of the micro-phase structure.