Synthesis And Characterization Of Proton Exchange Membranes Based On Sulfonated Poly (Phthalazinone Ether Sulfone Ketone)

Proton exchange membrane (PEM) is one of the key partments of Proton exchange membrane fuel cell (PEMFC). The property of PEM is the determinant of the performance of PEMFC. There are some disadvantages of Nafion membrane, such as high cost, high methanol permeability and poor resistance to methanol swelling and so on. Sulfonated poly (phthalazinone ether sulfone ketone)(SPPESK) is better than Nafion in terms of cost and methanol swelling. It is expected to use as the membrane in direct methanol fuel cell (DMFC). But the proton conductivity of SPPESK needs to improve.The casting solvents have some effects on the performance of membrane. The effect of solvents on the water uptake, swelling rate, conduction, ion exchange capability (IEC=mmol SO3H/g dry membrane) and methanol permeability of SPPESK were investigated. To improve the proton conductivity and tensile strain, the sulfonated poly (ether ether ketone) (SPEEK) with good water uptake was used to prepare SPPESK/SPEEK blend proton exchange membrane. To improve the water uptake and temperature resistance, the SPPESK/SiO2 compisite membrane was prepared by in situ sol-gel method.We prepared different sulfonation of SPPESKs by homogeneous sulfonation method using polyphthalazinone ether sulfone ketone (PPESK) as the raw material. The effects of solvents on the property of the membranes were investigated.1H-NMR spectroscopy revealed the information of a strong interaction between SPPESK and DMF, which decreased the proton conductivity and the ion exchange capability of the SPPESK membrane. The membrane produced by NMP owned the best water uptake, swelling rate and conduction, lower methanol permeability. The NMP was chosen for the solvent of SPPESK to produce proton exchange membranes.The water uptake, water swelling rate and proton conductivity of different sulfonation of SPPESK were investigated. The proton conductivity of SPPESK (DS=83%) was 0.1800 S cm-1 at 80℃, and the water swelling rate of this membrane was 26% at 80℃.To improve the proton conductivity of the membrane, we used the SPPESK (DS=83%) and the SPEEK with good water uptake to prepare the SPPESK/SPEEK blend proton exchange membrane. The results show that the water uptake and swelling rate of the SPPESK/SPEEK blend membrane are 101% and 34% at 80℃, respectively. The methanol swelling rate of the blend membrane is 20% at 80℃. The proton conductivity of the blend membrane is 0.212 S cm-1 at 80℃, which is 18% higher than that of SPPESK membrane. The flexibility of the blend membrane is also better than that of SPPESK membrane. The tensile strain increased from 16.48% to 30.43%.The SPPESK/SiO2 composite proton exchange membrane was prepared by the in situ hydrolytic polymerization of the Tetraethoxysilane (TEOS) using sol-gel method. The effect of the silica content in the composite membrane to the water uptake, water swelling rate, methanol swelling rate, methanol permeability and proton condunctivity of the membrane was investigated. The results show that, the methanol permeability of the composite membrane increased by the concent of silica increasing in the membrane. When the SiO2 content was lower than 8wt%, the conductivity increased as the SiO2 content increased. When the SiO2 content was higher than 8wt%, the conductivity decreased. The membrane with 8wt% SiO2 has the highest proton conductivity,0.238 S cm-1 at 80℃, which is 32% higher than that of SPPESK membrane. The water swelling rate was 33% at 80℃.