Synthesis And Characterization Of Fluorinated Poly(Aryl Ether Ketone) And Poly(Aryl Ether Sulfone) And Performance Study As Proton Exchange Membrane

Poly(aryl ether ketone)(PAEK) and poly(ary ether sulfone)(PAES) are very important high-performance polymers due to excellent comprehensive properties such as thermo-stability, mechanical, electrical and fire-retardant properties. Meanwhile, to prepare novel PAEK and PAES with good solubility and some new functions on the basis of retaining their inherent has become an important concern to exploit applications of this kind of high performance polymerical materials.To pursue good solubility, low dielectric constants and proton conductivity of PAEK and PAES, we commenced the design of design of monomers structure. Based on the synthesis of new monomers, a series of PAEKs and PAESs containing fluorinated in the side chain were prepared and characterized in this dissertation. The obtained polymers had good solubilities, themal and mechanical peoperties, low dielectrical constants and water uptake. Furthermore, novel sulfonated PAEKs and PAESs were prepared via direct polymerization. The sulfonated PAEKs and PAESs had high proton conductivity, moderate water uptake and low swelling ratio. PEMFC were assembled using sulfonated PAEK or PAES as proton exchange membranes, and the performances of fuel cells were studied. The main content is as follows:1. Two novel fluorinated bisphenol monomers (4-fluorophenyl)hydroquinone (3b) and (3,4-difluoro phenyl)hydroquinone (3c) were synthesized in two steps by the coupling reaction of (4-fluorophenyl)diazonium chloride and (3,4-difluorophenyl)-diazonium chloride with1,4-benzoquinone in the presence of NaHCO3to yield (4-fluorophenyl)benzoquinone (2b) and (3,4-difluorophenyl) benzoquinone (2c), respectively, followed by reduction with Zn/HCl. The chemical structures of the fluorinated bisphenol monomers were confirmed by FT-IR, NMR and elementary analysis.2. A series of PAEK (4a-c)/PAES (5a-c) with fluorinated phenyl in the side chain were synthesized from3b,3c, respectively, with4,4’-diflourobenzophenone (DFBP) and bis(4-chlorophenyl) sulfone (CDPS) via nucleophilic aromatic substitution polycondensation. The structures of the resulting polymers were characterized by FT-IR, NMR and elementary analysis. PAEK (4a-c), PAES (5a-c) had inherent viscosities ranging from0.50～0.92dL/g,0.62～0.81dL/g, respectively, which indicated the obtained polyerms had high molecular weights.3. The properties of the obtained polymers were investigated. Polymers4a-c,5a-c were soluble in normal solvents such as chloroform (CHCl3), dimethylsulfoxide (DMSO), N-methyl-2-pyrrolidone (NMP), N,N-dimethylacetamide (DMAc), N,N-dimethylformamide (DMF), tetrahydrofuran (THF) and concentrated sulphuric acid. They also showed good thermal stability with glass transition temperatures (Tg) beyond148℃, and10% weight loss temperatures in the range of541～606℃in nitrogen. The films of4a-c and5a-c possessed tensile strengths of88.1-104Mpa, Young’s moduli of2.68-3.52GPa, and elongations at break of15%-34%. Moreover, these polymers also displayed low dielectric constants of2.75-3.02(at1MHz) and low water absorptions.4. Sulfonated4,4’-diflourobenzophenone (SDFBP) were synthesized from DFBP and fuming sulfuric acid. Poly(ether ether ketone)s (SPAEK-1～5) containing sodium sulfonate groups were synthesized directly using SDFBP, DFBP and3b as comonomers. The sulfonation degree of the polymers was controlled between0.2-1.0by varying the molar ration of SDFBP and DFBP. The structures of the sulfonated PAEKs were confirmed well by FT-IR, NMR and elementary analysis. SPAEK-1～5had inherent viscosities ranging from1.06～1.78dL/g.5. The performances of SPAEK-1-5and their application in H2/O2single cell were explored. All the prepared SPAEKs could dissolve in NMP, DMSO and DMAc, swell in CHCl3, but not dissolve in water, methanol and acetone. The Tg s of all the sulfonated polymers were over176℃, and increased with increasing sulfonation degree. No obvious glass transition was observed for SPAEK-3～5in the range of 100～350℃. Two weight loss steps were observed in the TGA curves of SPAEK-1～5. corresponding to the decomposition of the sulfonic acid group and the main polymer chain, respectively. The films of SPAEK-1～5prepared by solution-casting had tensile strengths of50.5-70.4Mpa, Young’s moduli of1.04～1.97GPa, and elongations at break of12%～23%, which could meet the requirement in pratical application. The water uptake and swelling ration in liquid water increased with temperature and sulfonation degree. The water uptake and swelling ration were19.4%,1.3%respectively at30℃and57.5%,17.9% respectively at80℃. The proton conductivity of SPAEK-1-5also increased with sulfonation degree and temperature and reached to4.76×10-3～4×10-1S·cm-1at80℃. Under the same test condition the methonal permeability of these sulfonated PAEKs was1/12～1/8of Nafion’s. The membrane derived from SPAEK-4was used to fabricate MEA, and the MEA properties were then evaluated in single PEMFC. At room temperature the open-circuit voltage was982mV, and the highest power density was114.1mW/cm2.6. The synthesis of sulfonated bis(4-chlorophenyl) sulfone (SDCDPS) from DCDPS and fuming sulfuric acid. Poly(ether ether sulfone)s (SPAES-1～5) containing sodium sulfonate groups were synthesized directly using SCDPS, DCPS and3b as comonomers. The sulfonation degree of the polymers was controlled by varying the molar ration of SCDPS and DCPS. The structures of the sulfonated PAESs were confirmed well by FT-IR, NMR and elementary analysis.7. The properties of SPAES-1～5and their application in H2/O2single cell were studied. All the obtained SPAESs could dissolve in NMP, DMSO and DMAc, swell in CHCl3, but not dissolve in water, methanol and acetone. The Tg of SPAES-1was200℃, but no obvious glass transition was observed for SPAES-2-5in the range of100～350℃. There were two weight loss steps in the TGA curves of SPAEK-1～5, corresponding to the decomposition of the sulfonic acid group and the main polymer chain, respectively. The films of SPAES-1～5prepared by solution-casting had tensile strengths of47.3～63.5MPa, Young’s moduli of1.15～1.91GPa, and elongations at break of9.8%～13.2%. The water uptake and swelling ration in liquid water were greatly affected by sulfonation degree and temperature. For example, the water uptake of SPAES-5reached104.55%and its swelling ratio was30.28%at80℃. The proton conductivity of SPAES-1-5increased with sulfonation degree and temperature and reached to1.56×10-3～3.54×10-1S·cm-1at90℃. At the same test condition the methonal permeability of these sulfonated PAESs was1/12-1/7of Nafion’s.The MEA was assembled with membrane derived from SPAES-4,and the properties were then evaluated in single PEMFC. At room temperature the open-circuit voltage was1000.7mV, and the highest power density was120.6mW/cm2.