Novel sulfonated N-heterocyclic poly(aryl ether ketone ketone)s with pendant phenyl groups for proton exchange membrane performing enhanced oxidative stability and excellent fuel cell properties

Novel sulfonated poly(bis-phthalazinone ether ketone ketone)s containing pendant phenyl moieties (SP-BNPs) are prepared from poly (bis-phthalazinone ether ketone ketone)s containing pendant phenyl groups via post-sulfonated modification. The resulting polymers possess the ion exchange capacity ranging from 0.91 to 1.46 mmol g-1 and intrinsic viscosity scattering from 3.9 to 6.4 dL g-1. SP-BNPs membranes are manufactured using the solution-casting method with water absorption up to 17.1%. The swelling rate of SP-BNPs membranes is up to 5.6%, and the tensile strength is higher than 62 MPa. The proton conductivity ranges from 9.8 to 103 mS cm-1 at 75 °C. The breaking time of SP-BNPs membranes in Fenton's reagent at 80 °C is longer than 3 h. The result indicates that SP-BNPs membranes exhibit better oxidation stability than sulfonated poly(ether ether ketone)s and sulfonated poly(phthalazinone ether ketone) membranes. The peak power density of the cells equipped with SP-BNPs membranes is up to 1790 mW cm-2. The introduction of phthalazinone units and sulfonated pendant phenyl groups inhibits excessive water absorption in membranes, ensures efficient proton-conduction, and restrains the attack of radicals on the main chains. The combination of sulfonated pendant phenyl groups and twisted heterocyclic structures would enhance the oxidation stability and fuel-cell performance.