Highly conductive flexible alkylsulfonated side chains poly(phthalazinone ether ketone)s for proton exchange membranes

In this work, a series of long flexible alkylsulfonated side chains poly (phthalazinone ether ketone) (SFG-PPEK-x) are successfully synthesized through polycondensation , demethylation , and sulfobutylation grafting reaction to the polymer backbone. The resulting ionomers could dissolve in polar aprotic solvents , such as DMSO , NMP etc and show excellent film-forming properties. Furthermore, the effect of side chain lengths on the properties of the resulting PEMs, such as proton conductivity, water uptake, and swelling ratio are investigated systematically. The SFG-PPEK-4 membranes (IEC = 1.70 mmol g −1 ) show the highest proton conductivity in the range of 107 mS cm −1  at 30 °C and 184 mS cm −1  at 80 °C, which is higher than that of Nafion ® 115. The thermal, mechanical properties and chemical stability of SFG-PPEK-x are discussed, systematically.