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Synthesis and Characterization of Sulfonated Polyimide Containing S-triazine Moiety

Author: JiXiaoDong
Tutor: LiuCheng
School: Dalian University of Technology
Course: Polymer materials
Keywords: Sulfonated polyimide Aryl-s-triazine ring Synthesis Proton exchange membrane
CLC: TM911.4
Type: Master's thesis
Year: 2011
Downloads: 55
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Abstract


Proton exchange membrane fuel cell (PEMFC) is a highly efficient energy conversion device. The fuel cell has been gaining serious attention as a next-generation energy source owing to its advantages including high efficiency, high energy density, quiet operation, and environmental friendliness relative to conventional energy generators. The proton exchange membrane fuel cell (PEMFC) is considered to be the most promising power source for portable and automotive applications. One of the core components of PEMFC is the proton exchange membrane (PEM). Currently, the state-of-the-art PEMs are perfluorinated sulfonated ionomer membranes, such as Nafion(?). However, due to their high cost, fuel crossover and lower operation temperature have limited perfluorinated membranes’ applicability and triggered the quest for alternative membranes.Aromatic polyimide has excellent thermal’stability, high mechanical properties, good film-forming ability and superior chemical resistance, which has attracted widespread attention. Its excellent performance just meets the fuel cell membrane material requirements. Sulfonated polyimides have high proton conductivity and receive broad attention. However, the poor hydrolysis resistance limits their application. So, in this paper, with the help of the molecular design,, we synthesized a novel aromatic diamine containing triazine ring, and a series of sulfonated polyimides containing triazine ring structure, in order to improve their hydrolysis and thermal resistance.Firstly, we synthesized the dinitro-compound contained the triazine ring structure by one-step and two-step with p-nitrobenzonitrile, respectively. In the one-step synthesis, the synthesis technology was studied and the effect of technological parameters on the yield of target monomer has been studied thoroughly. However, it has poor reproducibility and low yield. So, we adopted the two-step method. The dinitro-compound was prepared by the intermediate of p-nitrobenzene and benzoyl chloride. And the synthesis technology of this reaction was studied. A optimized synthetuc conditions were obtained. Comparing these two methods, we found that dinitro monomer was synthesized in high yield and purity in the two-step synthesis method. Secondly, the monomer was reduction by alkali- and acid-catalytic reduction, respectively. The results showed that the product synthesized by. acid-catalytic reduction had higher yield and purity (99.15%), compared with the alkali-catalytic reduction. Finally,2,2’-sulfonic-4,4’-diaminodiphenyl ether monomers was synthesized by sulfonation. The structures of the intermediates and monomers were characterized by FT-IR,1H NMR and elemental analysis, which confirm their structures.The sulfonated polyimides were synthesized from the non-sulfonated diamine, sulfonated diamine and 1,4,5,8-naphthalenetetracrboxylic dianhydride (NTDA). The structure of SPIs was characterized by FT-IR and 1H NMR. The solubility was qualitative studied in common solvents. It found that SPIs can be soluble in DMSO and DMF, but not soluble in chloroform, acetone and m-cresol.. The thermal stability of SPIs was studied and the result shows that the pyrolysis of SPIs has three sections. The decomposition temperature of polymer main-chain is above 500℃and it shows a good high-temperature performance. The IEC of SPIs is between 0.60～1.80 mequiv·g-1. The oxidative resistance SPI membranes at room temperature and 80℃are above 20h. They have high water absorption but the low dimensional change. The result of the mechanical properties show that SPIs have the tensile strength of 45 MPa, and elongation at break ranging from 5.4～14.3%.

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CLC: > Industrial Technology > Electrotechnical > Independent power supply technology (direct power) > Chemical power sources,batteries, fuel cells > Fuel cell
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