Quaternized polyhedral oligomeric silsesquioxanes (QPOSS) modified polysulfone-based composite anion exchange membranes

A new method was applied to prepare a series of composite anion exchange membranes by incorporating quaternized polyhedral oligomeric silsesquioxanes (QPOSS) into the quaternized polysulfone (QPSU). The highly functional QPOSS were synthesized by epoxide ring opening reaction of Octaammonium POSS (OAPOSS) with glycidyltrimethylammonium chloride (GDTMAC). It has been shown that the hydroxide conductivity of composite membranes was significantly improved when the QPOSS was doped into the QPSU. Especially, the QPSU-3%-QPOSS exhibited 60% improvement in the hydroxide conductivity than that of the pure QPSU membrane and reached the highest value of 53.6 mS/cm at 80 °C. TEM characterizations indicated that the formed ion clusters and connected ion transport channels are responsible for the improvement of hydroxide conductivity. In addition, the water uptake, alkaline resistance and oxidative stability of composite membranes were also improved after the doping of QPOSS. The other properties of AEMs including mechanical property, thermal stability and methanol permeability were also investigated. Our study indicated that doping highly functional polyhedral oligomeric silsesquioxanes is a simple and effective method to improve the properties of the AEMs.