An intrinsic high-barrier polyimide (9-OH-FPPI) was prepared through the polycondensation reaction of pyromellitic dianhydride (PMDA) with a novel diamine (9-OH-FPDA) containing fluorenol moiety. The synthesized polyimide displays superior barrier performances, possessing water vapor transmission rate (WVTR) and oxygen transmission rate (OTR) low to 1.64 g·m⁻²·day⁻¹ and 0.66 cm³·m⁻²·day⁻¹, respectively. Meanwhile, 9-OH-FPPI also demonstrates high thermal stability with a glass transition temperature (T_g) of 410 °C, 5% weight-loss temperature (T_d5%) of 577 °C under N₂ and coefficient of thermal expansion (CTE) of 5.65 ppm/K. A detailed molecular simulation study as well as positron annihilation lifetime spectroscopy (PALS) and wide angle X-ray diffraction (WAXD) analysis have been carried out to reveal the barrier mechanism. The results reveal that the introduction of fluorenol moiety not only enhances the rigidity and regularity of polymer backbone, but also improves the interchain cohesion of PI matrix, which in turn lead to high crystallinity, low free volume and poor chains mobility of 9-OH-FPPI. The high crystallinity and low free volume decrease the diffusion and solubility of gases in polyimide matrix. In addition, the poor chains mobility further suppresses the gases diffusion. Simultaneous reductions of gases diffusion and solubility promote the barrier properties of 9-OH-FPPI. The as-synthesized polyimide exhibits wide application prospects in the flexible electronic packaging industry.

通过均苯四甲酸二酐（PMDA）与一种含有芴基的新型二胺（9-OH-FPDA）的缩聚反应制备了一种本征高阻聚酰亚胺（9-OH-FPPI）。合成的聚酰亚胺显示出优异的阻隔性能，分别具有低至1.64g·m ^-2 ·day ^-1和0.66cm ³ ·m ^-2 ·day ^-1的水蒸气透过率（WVTR）和氧气透过率（OTR）。同时，9-OH-FPPI还显示出高的热稳定性，在N ₂下的玻璃化转变温度（T _g）为410°C，5％失重温度（T _d5％）为577°C，并且热膨胀系数为（CTE）为5.65 ppm / K。进行了详细的分子模拟研究以及正电子an没寿命谱（PALS）和广角X射线衍射（WAXD）分析，以揭示阻挡层机理。结果表明，芴基部分的引入不仅增强了聚合物主链的刚性和规则性，而且还改善了PI基体的链间内聚力，进而导致9-OH-的高结晶度，低自由体积和较差的链迁移率FPPI。高结晶度和低自由体积降低了气体在聚酰亚胺基体中的扩散和溶解度。另外，不良的链迁移率进一步抑制了气体扩散。气体扩散和溶解度的同时降低促进了9-OH-FPPI的阻隔性能。