| Proton exchange membrane fuel cell(PEMFC) is a kind of environmental and efficiency energy resource where the proton exchange membrane(PEM) serves as one of its key components. In this dissertation, a difluoride monomer containing sulfonated side-chain was synthesized and a series of side-chain type sulfonated poly(arylene ether sulfone)s were prepared. The tough, flexible, and transparent membranes were obtained by casting polymer solution onto glass plate. The physical and chemical properties of these membranes were investigated in ion-exchange capacity, water uptake, dimensional stabilities, mechanical properties and proton conductivity, etc.Bis(4-fluoro-2-benzoyl)phenyl sulfone(BFBPS) with benzoyl groups in sulfone ortho position was successfully synthesized under catalysis of cuprous iodide by benzoyl chloride reacted with an organic zinc intermediate which was prepared by lithium-zinc substitution reaction from 4-fluorophenyl sulfone(DFDPS) through metal lithium reaction. Sulfonated monomer bis(4-fluoro-2-(3-sulfonic benzoyl)) phenyl sulfone(BFSBPS) was obtained by sulfonation BFBPS with fuming sulfuric acid. A series of side-chain proton exchange membranes based on sulfonated poly(arylene ether sulfone)s with different ion exchange capacity(IEC) were prepared by direct aromatic nucleophilic substitution polycondensation of BFSBPS, DFDPS and 4,4-biphenol(BP). A series of main-chain sulfonated poly(arylene ether sulfone)s were prepared based on the monomer bis(4-fluoro-3-sulfonic sodium phenyl)sulfone for comparation. Two multi-block side-chain type sulfonated proton exchange membranes with different IEC value were prepared. The primary basic properties were investigated.The thermal stability of the side-chain sulfonated poly(arylene ether sulfone)s copolymers showed high thermal stability with decomposition temperature above 320°C. These proton exchange membranes have the maximum tensile strength above 50 MPa, Young modulus above 1.0 GPa. Water uptake and dimensional change indicated that the proton exchange membranes increased with the increase of membrane IEC values. The side chain type membranes showed anisotropy in dimensional change and more obvious for that of the multi-block side-chain type membranes, when compared to the main-chain ones. The main-chain type membranes exhibited higher water uptake compared with the side-chain type ones. The multi-block side-chain type membranes showed the highest water uptake.The side-chain type membranes exhibited higher proton conductivity than that of main-chain type ones. For example, the side-chain type membrane with IEC of 1.32 meg/g showed higher proton conductivity(56 mS cm-1) than that of the main-chain membrane(47 mS cm-1) with the similar IEC of 1.41 meg/g. The sulfonic acid groups on the side-chain have a distance with the polymer chain, the higher activities of sulfonic acid groups formed a wide range of hydrophilic regions, which is helpful for the proton conductivity in the membranes. Multi-block side-chain type membranes easily formed hydrophilic /hydrophobic phase separation region. Hydrophilic region easily merged with each other to form proton transmission channel. Multi-block side-chain type membranes exhibited the highest proton conductivity than other proton exchange membranes. |
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