Abstract: Colourless polyimide (CPI) is widely used as covers, substrates and touch panels for flexible displays, which require high glass transition temperatures (Tg), low coefficients of thermal expansion, excellent optical transparency and good mechanical properties. CPI is mainly obtained by introducing fluorine-containing groups to change the chemical structure of the molecular chain. This method of preparation allows for the production of CPI with high light transmittance, although it concomitantly results in a reduction in thermal and mechanical properties. By modifying two-dimensional inorganic materials, the thermal and mechanical properties of CPI can be effectively improved. However, technical difficulties such as poor compatibility with CPI and the complicated modification process also limit the application of two-dimensional inorganic materials in CPI modification. Therefore, a new method for modifying of CPI by a two-dimensional organic polymer, a two-dimensional polyaramid (2DPA) was proposed in this study, 2DPA/CPI composite films were prepared by the solution phase mixing method and the two-step thermoimide method. The structure and properties of 2DPA were analyzed, and the effects of 2DPA additives on the properties of 2DPA/CPI composite films, such as light transmittance, water absorption, Tg, and tensile strength were investigated. The results showed that without compromising the light transmission, the best effect was achieved when the addition of 2DPA in 2DPA/CPI composite films was 1wt%, and the Tg was increased from 338℃ to 358℃ compared to that of CPI films. The tensile strength reached 71.44 MPa, and elongation at break reached 4.34%, which were increased by 21.37% and 24.36%, respectively; and the water absorption rate was reduced by 39%, from 3.33% to 2.03%. The successful preparation of this CPI composite modified with two-dimensional organic material offers new ideas for the research and application of high-performance CPI-based composite materials, holding significant research value.

Key words: colorless polyimide, composite film, two-dimensional polyaramid, water absorption, glass transition temperature, tensile properties

摘要： 无色聚酰亚胺(CPI)广泛用作柔性显示器件的盖板、基板以及触控层面板，这些领域要求CPI具有高玻璃化转变温度(Tg)、低热膨胀系数、出色的光学透明度以及良好的力学性能。CPI主要通过引入含氟基团改变分子链的化学结构的方法获得，这种方法制备可以得到透光率高的CPI，但同时也会造成其热性能和力学性能的下降。二维无机材料改性的方法可以有效改善CPI的热学和力学性能。然而，与CPI相容性差、改性工艺复杂等技术难题也限制了二维无机材料在CPI改性中的应用。基于此，本研究提出二维有机聚合物——二维聚酰胺(2DPA)改性CPI的新方法，并通过溶液相混法和两步热酰亚胺法制备了2DPA/CPI复合薄膜。分析了2DPA的结构及性能，并探究了2DPA添加量对2DPA/CPI复合薄膜的透光率、吸水率、Tg和拉伸强度等性能的影响规律。结果表明，在不影响透光率的情况下，2DPA/CPI复合薄膜中2DPA的添加量为1wt%时效果最佳，与CPI膜相比，Tg从338℃提高至358℃；拉伸强度达到了71.44 MPa，断裂伸长率达4.34%，分别提升了21.37%和24.36%；吸水率降低了39%，由3.33%降至2.03%。这种二维有机材料改性CPI复合材料的成功制备，为高性能CPI基复合材料的研究与应用提供了新思路，具有重要的研究意义。

关键词: 无色聚酰亚胺, 复合薄膜, 二维聚酰胺, 吸水率, 玻璃化转变温度, 拉伸性能