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从分子设计出发,用不同的二胺单体和相同的二酐单体合成聚酰胺酸并制备聚合物膜。采用热重、热重-质谱、红外和X射线光电子能谱分析聚酰胺酸在热解过程中的结构变化及机理。结果表明,在热解过程中,聚酰胺酸的热解包括4个阶段,经吸附水和吸附氧的脱除及溶剂挥发,亚胺化,交联,以及高温阶段的主链断裂、脱氧、脱氢、芳构化等热解过程转化为无定形炭结构。前驱体的结构不同导致热解过程存在差异。PPD-PMDA和TMPPD-PMDA热解时所需的温度较高。其它聚酰亚胺析出CH4、CO2、C6H6的温度顺序为ODA-PMDA>BDAF-PMDA>BAPP-PMDA。在700℃热解后,BDAF-PMDA所含的氟元素基本消失。这表明聚酰亚胺的化学结构对炭膜的微结构有较大影响。
Starting from molecular design, polyamic acid was synthesized with different diamine monomers and the same dianhydride monomer and a polymer membrane was prepared. Thermogravimetry, TG-MS, IR and X-ray photoelectron spectroscopy were used to analyze the structure and mechanism of polyamic acid during pyrolysis. The results showed that the pyrolysis of polyamic acid in the pyrolysis process includes four stages: the removal of adsorbed water and adsorbed oxygen, the volatilization of solvents, imidization, cross-linking and the cleavage of the main chain in the high temperature stage, Dehydrogenation, aromatization and other pyrolysis process into amorphous carbon structure. Differences in the structure of the precursors lead to pyrolysis processes. The temperatures required for PPD-PMDA and TMPPD-PMDA pyrolysis are higher. The order of temperature for the other polyimides to precipitate CH4, CO2 and C6H6 is ODA-PMDA> BDAF-PMDA> BAPP-PMDA. After pyrolysis at 700 ℃, fluorine contained in BDAF-PMDA disappeared. This indicates that the chemical structure of the polyimide has a great influence on the microstructure of the carbon film.