Polymer ( IF 4.6 ) Pub Date : 2022-11-15 , DOI: 10.1016/j.polymer.2022.125528 Min Zhao, Caili Zhang, Yunxuan Weng, Pei Li
Thermal oxidative crosslinking results in the generation of oxygen bridges among polymer chains and helps regulate the membrane microstructure. Simultaneously, any strategy to increase the crosslinking sites of polyimide (PI) can improve the crosslinking efficiency and allow precise control of the pore structure of membranes. Phenolphthalein-based PIs are potentially suitable precursors for thermal oxidative crosslinking of membranes, since thermal treatment will result in the degradation of lactone ring leading to the generation of a pair of phenyl crosslinking sites. In this work, three phenolphthalein-based diamines with different structures were designed and synthesized. The three diamines were subsequently reacted with 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA) to prepare phenolphthalein-based PIs. The original membranes were post-treated by thermal oxidation crosslinking at 400 °C and 425 °C, respectively; the lactone ring underwent decomposition, and the imide ring opened at the same time, resulting in the generation of multiple crosslinking sites and correspondingly improving the crosslinking efficiency. The effect of the side groups (−CH3, –CF3 or unsubstituted) of phenolphthalein-based diamine and thermal treatment temperatures on the gas separation performance of phenolphthalein-based PI membranes were investigated. Wide-angle X-ray diffractometry (WAXD) and wide-angle X-ray scattering (WAXS) analysis demonstrated that the π-π stacking distance were improved. BTDA-FPP-425 had a CO2/CH4 selectivity of 37.68. This thermal degradation along with thermal oxidative crosslinking strategy provides a promising approach for fabrication of CO2/CH4 separation membrane.
中文翻译:
热分解和热氧化交联协同改善酚酞基聚酰亚胺膜CO2/CH4分离性能
热氧化交联导致聚合物链之间产生氧桥,并有助于调节膜的微观结构。同时,任何增加聚酰亚胺(PI)交联位点的策略都可以提高交联效率并精确控制膜的孔结构。基于酚酞的 PI 可能是膜热氧化交联的合适前体,因为热处理会导致内酯环降解,从而产生一对苯基交联位点。在这项工作中,设计并合成了三种具有不同结构的酚酞基二胺。这三种二胺随后与 3,3',4,4'-二苯甲酮四甲酸二酐 (BTDA) 反应制备酚酞基 PI。原膜分别在400℃和425℃进行热氧化交联后处理;内酯环发生分解,酰亚胺环同时打开,产生多个交联位点,相应地提高了交联效率。侧基的影响(-CH3 , –CF 3或未取代)的酚酞基二胺和热处理温度对酚酞基PI膜气体分离性能的影响。广角 X 射线衍射 (WAXD) 和广角 X 射线散射 (WAXS) 分析表明,π-π 堆积距离有所改善。BTDA-FPP-425 具有 37.68 的 CO 2 /CH 4选择性。这种热降解以及热氧化交联策略为制造 CO 2 /CH 4分离膜提供了一种有前途的方法。