Developing a polysulfone-based alkaline anion exchange membrane for improved ionic conductivity

Alkaline anion exchange membranes of high ionic conductivities were made from polysulfone by adding a chloromethyl pendant group to the polysulfone at different reaction times and temperatures, followed by reacting the chloromethyl group with different amines to form different quaternary ammonium pendant groups which acted as the counterion for hydroxide anion. The effects of temperature and time on chloromethylation of the polymer were investigated and the chloromethylation was optimized. Furthermore, different approaches for quaternization of the synthesized chloromethylated polymer were studied. The results show that both temperature and time exhibited significant impacts on chloromethylation and gelation. It was also found that using an appropriate quaternization approach could significantly improve the ionic conductivity and also could optimize the conductivity of the membrane even though the accessible functional chloromethyl groups were limited. The developed AAEM showed the ionic conductivity up to 3.1 × 10−2 S/cm at room temperature. Increasing temperature increased the ionic conductivity up to 7.33 × 10−2 S/cm. The formed AAEM was stable in a concentrated base up to 8.0 M KOH at room temperature.