A series of acyloxy-containing fluorene-based Cardo polyimides (PIs) were facilely synthesized by the post-polymerization modification based on a simple esterification of hydroxyl-containing PIs. Incorporation of acyloxy groups may reduce the packing density of PI chains and weaken both inter- and intra-chain charge transfer complexes (CTC) formation. Accordingly, the modified PIs exhibit the improved solubility in low-boiling-point solvents and optical transparence. The optical transmittance at 400 nm (T₄₀₀) of all modified PI films is significantly increased to 80.1–83.5% from 41.6–54.5% of the precursor PI films. Meanwhile, the modified PI films exhibit a bright fluorescence. The modified PIs still display the superior heat resistance with a glass transition temperature (T_g) of 301.1–390.9 °C as well as admirable mechanical properties with a tensile strength (T_S) of 72.1–81.3 MPa. In addition, the dielectric constant (k) value at 1 MHz of the modified PI films is decreased to 2.58–2.90 from 3.95–4.48 of the precursor PI films, which is attributed to the enlarged free volume and reduced water absorption afforded by the incorporation of acyloxy groups. This work provides an efficient post-polymerization modification approach to simultaneously affording the multifunctional PI films with high T_g, high T₄₀₀ and low k, probably as the potential candidates for the practical application in display and microelectronic industries.

通过基于含羟基 PI 的简单酯化的后聚合改性，轻松合成了一系列含酰氧基的芴基 Cardo 聚酰亚胺 (PI)。引入酰氧基可能会降低 PI 链的堆积密度并削弱链间和链内电荷转移复合物 (CTC) 的形成。因此，改性 PI 在低沸点溶剂中的溶解度和光学透明度都有所提高。所有改性 PI 薄膜在 400 nm ( T ₄₀₀ ) 处的透光率从前体 PI 薄膜的 41.6-54.5% 显着增加到 80.1-83.5%。同时，改性 PI 薄膜显示出明亮的荧光。改性 PI 仍然显示出优异的耐热性，玻璃化转变温度 ( T_克）的301.1-390.9℃，以及用拉伸强度（极佳的机械性能Ť_小号72.1-81.3兆帕）。此外，改性 PI 薄膜在 1 MHz 时的介电常数（ k）值从前体 PI 薄膜的 3.95-4.48 降低至 2.58-2.90，这归因于掺入提供的自由体积增大和吸水率降低酰氧基。这项工作提供了一种有效的聚合后改性方法，可以同时提供具有高T _g、高T ₄₀₀和低k的多功能 PI 薄膜，可能作为显示和微电子行业实际应用的潜在候选者。