An intrinsic high‐barrier polyimide (2,7‐CPAPPI) containing rigid planar carbazole moiety and amide group in main chain was prepared. The 2,7‐CPAPPI shows very attractive barrier performances, possessing water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) low to 0.04 g m⁻² day⁻¹ and 0.11 cm³ m⁻² day⁻¹, respectively. Meanwhile, 2,7‐CPAPPI also displays exceptional thermal stability with a glass transition temperature (T_g) of 552°C and coefficient of thermal expansion (CTE) of 15.48 ppm/K. The barrier performances of 2,7‐CPAPPI are compared with those of a structural analog (2,7‐CPPI, containing only carbazole moiety in the main chain) and a typical polyimide (Kapton). The structure–barrier performances relationship was investigated by molecular simulations, wide angle X‐ray diffraction (WAXD), and positron annihilation lifetime spectroscopy (PALS). The results show that 2,7‐CPAPPI has more number of intermolecular hydrogen bonds among the three PIs, which leads to close chain packing and thereby high crystallinity, low free volume, and poor chains mobility. That is, the high crystallinity and low free volume of 2,7‐CPAPPI decrease the diffusion and solubility of gases. Meanwhile, the poor chains mobility further reduces the gases diffusion. The decreased diffusion and solubility of gases consequently promote the improvement of barrier properties for 2,7‐CPAPPI.

中文翻译：

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主链上含有咔唑基团和酰胺基的高阻聚酰亚胺的合成，性质和分子模拟

制备了一个内在的高阻聚酰亚胺（2,7-CPAPPI），其主链中包含刚性平面咔唑部分和酰胺基。2,7-CPAPPI具有非常吸引人的阻隔性能，分别具有低至0.04 g m ^-2天^-1和0.11 cm ³ m ^-2天^-1的水蒸气透过率（WVTR）和氧气透过率（OTR）。同时，2,7-CPAPPI还显示出出色的热稳定性，玻璃化转变温度（T _g）为552°C，热膨胀系数（CTE）为15.48 ppm / K。将2,7-CPAPPI的阻隔性能与结构类似物（2,7-CPPI，在主链中仅包含咔唑部分）和典型的聚酰亚胺（Kapton）进行了比较。通过分子模拟，广角X射线衍射（WAXD）和正电子an没寿命谱（PALS）研究了结构与壁垒性能的关系。结果表明，2,7-CPAPPI在三个PI中具有更多的分子间氢键，这导致紧密链堆积，从而导致高结晶度，低自由体积和较差的链迁移率。也就是说，2,7-CPAPPI的高结晶度和低自由体积会降低气体的扩散和溶解度。同时，不良的链迁移率进一步降低了气体扩散。