含二氮芴可溶聚苯并咪唑的合成与性能研究

发布时间：2018-06-28 20:07

  本文选题：聚苯并咪唑 + 二氮芴　； 参考：《兰州大学》2017年硕士论文

【摘要】：芳香型聚苯并咪唑(PBI)具有良好的热化学稳定性和力学性能,广泛应用于耐火纤维,防腐涂层,航空航天及燃料电池等领域。在PBI结构中,弱碱性咪唑环可吸附磷酸,从而具备质子传导能力,因此磷酸掺杂聚苯并咪唑薄膜被看作是最具潜力的高温质子交换膜。但是,传统聚苯并咪唑因其刚性结构而导致较差的溶解加工性能,极大地限制了其实际应用。因此,研究制备新型易溶可加工聚苯并咪唑具有重要的实际意义。本文从分子结构设计出发,通过合成四胺、二酸单体,成功将吡啶,醚键,大体积的苯侧基和扭曲、非共面的二氮芴Cardo结构引入聚苯并咪唑主链,得到了一系列机械性能、热化学稳定性良好的易溶聚苯并咪唑,通过磷酸掺杂,所得质子交换膜具有良好的质子传导率和稳定性。主要研究内容如下:1、制备了含扭曲非共面结构的Cardo型芳香二酸单体:9,9-双(4-羧苯基)-4,5-二氮芴。并与2,6-双(3,4-二氨基苯基)-4-苯基吡啶通过程序升温法制备了易溶聚苯并咪唑聚合物。对比两种不同结构的四胺单体3,3',4,4'-联苯四胺与2,6-双(3,4-二氨基苯基)-4-苯基吡啶对聚合物性能的影响,阐明非共面结构对聚苯并咪唑溶解性的影响。结果表明,该新型聚苯并咪唑在常温下在多种常用极性非质子有机溶剂(如DMF、DMAc、DMSO、NMP)中有优异的溶解性。而且芳杂环的引入并没有减弱该聚合物的热、化学稳定性,制备的两种聚合物薄膜5%热损失温度为318 oC,10%热损失温度为540 oC。另外,在5 mol/L的磷酸溶液中,吡啶四胺结构聚苯并咪唑(PyTAB-PBI)磷酸掺杂水平达到8.12,高于联苯四胺结构聚苯并咪唑(TAB-PBI)的6.40,其质子传导率也由0.046 S cm-1提高到0.068 S cm-1。2、通过分子结构设计,制备了含醚及二氮芴Cardo型芳香二酸单体:9,9-双(4-羧苯氧基)-4,5-二氮芴,以此将柔性醚键引入聚苯并咪唑分子主链,改善分子链的柔性,使分子链容易翻转,增加分子链间的距离,从而减小分子链间的相互作用力,改善其溶解性能。醚键的存在导致该聚合物热稳定性有略微降低,5%热损失温度为204 oC。另外,聚苯并咪唑薄膜通过不同浓度(5、7、9、11 mol/L)的磷酸掺杂测试表明,在9 mol/L的磷酸溶液中,该膜磷酸掺杂水平达到12.37,在干燥状态,180 oC时质子传导率为0.072 S cm-1。3、通过分子结构设计,合成侧链含有羟基的四胺单体:2,6-双(3,4-二氨基苯基)-4-羟苯基吡啶。在聚苯并咪唑侧链引入羟基,与主链的咪唑环形成离子交联结构。分子间的氢键存在使膜的溶解性能有所降低,溶解性测试表明在羟基含量高于60%时,聚合物在加热至100 oC后才可以完全溶解。交联结构增强了膜的尺寸稳定性,侧链含羟基的PBI膜比不含羟基的PBI膜溶胀率降低30%左右。聚合物侧链的羟基易磷酸分子之间形成桥联结构,使一部分磷酸分子固定在分子链上,磷酸掺杂水平较不含羟基PBI膜略微提高。
[Abstract]:Aromatic polybenzimidazole (PBI) has good thermochemical stability and mechanical properties. It is widely used in refractory fibers, anticorrosive coatings, aerospace and fuel cells. In PBI structure, phosphoric acid can be adsorbed by weak basic imidazole ring, which has the proton conduction ability. Therefore, phosphoric acid doped polybenzimidazole film is considered as the most potential high temperature proton exchange membrane. However, due to its rigid structure, traditional polybenzimidazole has poor solubility and processing performance, which greatly limits its practical application. Therefore, it is of great practical significance to study the preparation of new soluble and processable polybenzimidazole. Based on the molecular structure design, a series of mechanical properties of polybenzimidazole were obtained by synthesizing tetraamine, diacid monomer, pyridine, ether bond, large volume benzyl side group and twisted, non-coplanar fluorene Cardo structure into the main chain of polybenzimidazole. The readily soluble polybenzimidazole with good thermochemical stability was prepared by phosphoric acid doping and the proton exchange membrane had good proton conductivity and stability. The main contents of this study are as follows: 1. Cardo aromatic diacid monomers with distorted noncoplanar structure: 1. 9- (4-carboxyphenyl) -4- (4-) -5-diazofluorene was prepared. The soluble poly (benzimidazole) polymer was prepared by temperature-programmed method with 2o 6 bis (3 O 4 diaminophenyl) -4 phenyl pyridine. The effects of two kinds of tetraamine monomers, 3- (3-)-(3-)-(4-diaminophenyl) -4-phenyl-pyridine, on the solubility of poly (benzimidazole) were compared with those of 2o _ 6bis (3o _ 4-diaminophenyl) -4-phenylpyridine. The effect of non-coplanar structure on the solubility of polybenzimidazole was discussed. The results show that the novel polybenzimidazole has excellent solubility in a variety of commonly used polarity non-proton organic solvents such as DMFX DMAC DMSON NMP at room temperature. Moreover, the introduction of aromatic heterocycles did not weaken the thermal and chemical stability of the polymer. The 5% heat loss temperature of the two polymer films was 318 OC 10% and the heat loss temperature was 540 OC. In addition, in 5 mol / L phosphoric acid solution, the phosphoric acid doping level of PyTAB-PBI was 8.12, which was higher than that of TAB-PBI (6.40), and the proton conductivity was increased from 0.046 S cm-1 to 0.068 S cm-1.2. In this paper, the ether and fluorene Cardo aromatic diacid monomer: 9 ~ 9- bis (4-carboxyphenoxy) -4o _ 5- diazofluorene was prepared. The flexible ether bond was introduced into the main molecular chain of poly (benzimidazole), which improved the flexibility of the molecular chain, made the molecular chain easy to flip and increased the distance between the molecular chains. Therefore, the interaction force between molecular chains is reduced and the solubility is improved. The presence of ether bond leads to a slight decrease in the thermal stability of the polymer by 5% to 204 OC. In addition, the phosphoric acid doping of polybenzimidazole thin films at different concentrations (5 ~ 7 ~ 9 ~ 9 ~ 11 mol / L) shows that in 9 mol / L phosphoric acid solution, the phosphoric acid doping level of the film is 12.37, and the proton conductivity is 0.072 S ~ (cm ~ (-1) at a dry state of 180oC, which is designed by molecular structure. In this paper, a tetraamine monomer with hydroxyl groups in the side chain was synthesized. The hydroxyl group was introduced into the side chain of polybenzimidazole and the ionic crosslinking structure was formed with the imidazole ring of the main chain. The solubility of the membrane was decreased by the existence of hydrogen bond between molecules. The solubility test showed that when the hydroxyl content was higher than 60 鈩，

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