Liu Yiwu, Xie Fengyun, Huang Jie, Tan Jinghua, Chen Chengliang, Jiang Linbing, Sun Wei, Zhang Hailiang
National and Local Joint Engineering Center of Advanced Packaging Materials R & D Technology, Key Laboratory of Advanced Packaging Materials and Technology of Hunan Province, School of Packaging and Materials Engineering, Hunan University of Technology, Zhuzhou 412007, China.
Key Laboratory of Polymeric Materials and Application Technology of Hunan Province, Key Laboratory of Advanced Functional Polymer Materials of Colleges, Universities of Hunan Province, College of Chemistry, Xiangtan University, Xiangtan 411105, China.
Polymers (Basel). 2021 May 27;13(11):1749. doi: 10.3390/polym13111749.
A novel carbazole-containing diamine (M-2,7-CPDA) isomer of our previously reported diamine 2,7-CPDA, has been synthesized using a two-step synthesis. Compared with 2,7-CPDA, the substituted position of amino is changed from to for M-2,7-CPDA. The two diamines were polymerized with pyromellitic dianhydride (PMDA) to prepare two isomeric polyimides (M-2,7-CPPI and 2,7-CPPI), respectively. The effects of isomerism on microstructures and gas barrier performances of the two isomeric polyimides were studied by positron annihilation test, X-ray diffraction and molecular simulation. The results display that -connected M-2,7-CPPI has less ordered chain structure and weaker hydrogen bonding than -connected 2,7-CPPI, which leads to loose chain stacking and thereby increased free volumes of M-2,7-CPPI. The higher free volumes promote the solubility and diffusivity of gas in M-2,7-CPPI. As a result, the -linked M-2,7-CPPI shows a lower gas barrier than its -linked analog. The work provides guidance for the design and synthesis of high-performance barrier polymers.
我们之前报道的二胺2,7 - CPDA的一种新型含咔唑二胺（M - 2,7 - CPDA）异构体已通过两步合成法合成。与2,7 - CPDA相比，M - 2,7 - CPDA的氨基取代位置发生了变化。将这两种二胺分别与均苯四甲酸二酐（PMDA）聚合，制备了两种异构聚酰亚胺（M - 2,7 - CPPI和2,7 - CPPI）。通过正电子湮没测试、X射线衍射和分子模拟研究了异构现象对这两种异构聚酰亚胺微观结构和气体阻隔性能的影响。结果表明，与相连的2,7 - CPPI相比，相连的M - 2,7 - CPPI具有较少的有序链结构和较弱的氢键，这导致链堆积松散，从而增加了M - 2,7 - CPPI的自由体积。较高的自由体积促进了气体在M - 2,7 - CPPI中的溶解性和扩散性。因此，相连的M - 2,7 - CPPI的气体阻隔性低于其相连的类似物。这项工作为高性能阻隔聚合物的设计和合成提供了指导。
