| Summary: | 博士 === 國立臺灣科技大學 === 材料科學與工程系 === 101 === This dissertation includes two parts. First part is “Synthesis, Characterization and Hydrolysis of Aromatic Polyazomethines Containing Non-Coplanar Biphenyl Structures”. Second part is “Synthesis, Characterization and Proton Exchange Membrane Fuel Cell Applications of Novel Polybenzimidazole Containing 2,2’-Disubstituted-4,4’-diphenylether Moiety”.
In the first part, new polyazomethines containing electron-withdrawing trifluoromethyl group and non-coplanar biphenyl structures were prepared at room temperature under reduced pressure. It was found that these polyazomethines would undergo hydrolysis in DMSO solution at temperature higher than 50 oC. The hydrolysis, evidenced by 1H NMR spectra and GPC chromatograms, was resulted from the reverse reaction of azomethine formation and was facilitated at higher temperature. The GPC results also suggested that post-polymerization would be possible if polyazomethine films were heated at elevated temperature (200 oC) under reduced pressure (0.27 torr). The HOMO (-5.69 to -5.96 eV) and LUMO (-3.04 to -3.18 eV) energy levels of the new polyazomethines are much lower than those of other polyazomethines. Combined with the excellent solubility and good thermal stability, non-coplanar biphenyl structure containing electron-withdrawing trifluoromethyl group could be a new candidate as electron acceptor for the structure design of new conjugated polymers.
In the second part, A novel tetraamine containing 4,4’-diphenylether moiety and phenyl ring as side group was prepared via eight steps from 4,4’-oxydianiline (4,4’-ODA). It was found that side acylation reaction of polybenzimidazole would take place during polycondensation under appropriate conditions. The novel tetraamine which had phenyl ring at 2 and 2’ positions provides more opportunities for side acylation reaction. According to the competition of side acylation reaction and linear polymerization, high-molecule weight polybenzimidazole could not be obtained when this novel tetraamine was used. PBI-7 was synthesized from commercial 3,3’-diaminobenzidine and novel diacid which had 4,4’-diphenylether moiety and bromine group at 2 and 2’ position. It exhibited excellent solubility in common organic solvents and good thermal stability. The decomposition temperature at 5% weight loss under nitrogen was 439oC。The proton exchange memebrane of PBI-7 was prepared in 3% (by weight) NMP solution. The phosphoric acid doping level is 6.9 and phosphoric acid doped weight percent is 221% at room temperature. The proton conductivity of PBI-7 is 9.0 × 10-3 (S/cm) at 80 oC and 2.6 × 10-2 (S/cm) at 160 oC. The activation energy of proton conductivity which was calculated from Arrhenius equation is 21.12 (kJ/mol). Combined with the excellent solubility, good thermal stability and proton conductivity, PBI-7 containing 4,4’-diphenylether moiety and bromine group at 2 and 2’ position could be a new material as proton exchange membrane for fuel cell applications.
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