The macromolecular chain of conventional polyimide (PI) is a predominant linear extension, which is anticipated to uphold robust interchain interactions essential for preserving overall mechanical and thermal performance. This study is dedicated to the design and synthesis for the novel PIs containing folded chains, with a particular emphasis on modifying the chain conformational behavior with respect to the structure of the aggregation state and the corresponding gas separation properties. First, two unidirectional diamine monomers, dibenzo [c, g] phenanthrene-9,12-diamine (NPDA) and anthracene-1,8-diamine (ADA), were meticulously synthesized through a sequence of chemical reactions, including Witting olefination and photocyclization. These monomers possess distinctive spatial characteristics: NPDA adopts a helical conformation, while ADA maintains a planar structure. Subsequently, the corresponding folded chain-containing PIs, denoted as NPI and API, were successfully achieved by copolymerizing one of the unidirectional monomers with the 6FDA-TPDA system. API and NPI generally exhibit a propensity for enhanced molecular chain stacking, while retaining their good solubility and processability. Drawing from both experimental data and simulation results, it was ascertained that the inclusion of these two monomers produces a rearrangement of pore sizes with a decrease in large-size micropores and an increase in the percentage of ultra-micropores. Moreover, the PI membranes with the folded fragments have a much better CO2 plasticization resistance.

中文翻译：

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具有刚性折叠片段的聚酰亚胺的合成和表征


传统聚酰亚胺 （PI） 的大分子链是一种主要的线性延伸，预计它将维持强大的链间相互作用，这对于保持整体机械和热性能至关重要。本研究致力于设计和合成包含折叠链的新型 PI，特别强调改变与聚集态结构和相应的气体分离特性相关的链构象行为。首先，通过一系列化学反应精心合成了两种单向二胺单体，二苯并 [c， g] 菲-9,12-二胺 （NPDA） 和蒽-1,8-二胺 （ADA），包括 Witting 烯化和光环化。这些单体具有独特的空间特性：NPDA 采用螺旋构象，而 ADA 保持平面结构。随后，通过将其中一种单向单体与 6FDA-TPDA 系统共聚，成功实现了相应的折叠链含链 PI，表示为 NPI 和 API。API 和 NPI 通常表现出增强分子链堆叠的倾向，同时保持其良好的溶解度和可加工性。从实验数据和模拟结果中，可以确定这两种单体的加入会产生孔径的重排，大尺寸微孔减少，超微孔百分比增加。此外，带有折叠片段的 PI 膜具有更好的 CO2 塑化性。