Surface hydrophilization toward the proton conductive porous PTFE substrate impregnating SPEEK for polymer electrolyte membranes

Porous poly(tetrafluoroethylene) (PTFE) substrate was impregnated with sulfonated poly(ether ether ketone) (SPEEK) molecules to synthesize the reinforced polymer electrolyte membranes with high dimensional stability and high proton conductivity. During the hydrophilization of the hydrophobic PTFE pore surface with hydroquinone/polyethyleneimine mediator for feasible impregnation of SPEEK molecules, alendronic acid was introduced along to enhance the proton conductivity of the membrane. The chemical composition, morphology, and hydrophilicity of the membrane were examined by XPS, FESEM, and water contact angle measurements to analyze its surface modification effect. Water uptake, swelling ratio, mechanical strength, and proton conductivity of the pore filled membranes were investigated for their application of fuel cell. While the swelling ratio of pore filled membrane was even lower than that of Nafion117 at all temperatures (<15% even at 80 °C), its proton conductivity was comparable to that of Nafion 117. The tensile strength of pore filled membrane, 23.13 MPa, was much higher than that of the pristine SPEEK70 membrane, 12.4 MPa, but similar to that of Nafion in hydrated states.