Polyimides (PIs) have attracted great attention because of their excellent properties and applications in areas such as flexible display substrates, microelectronics, and integrated circuits. The effects of crosslinking on the thermal, mechanical, and dielectric properties of PIs, however, still require further investigation. In this work, we introduce a crosslinkable monomer, bicyclo[2.2.2]oct-7-ene-2,3,5,6-tetracarboxylic acid dianhydride (BTA), which contains double bonds, into the system consisting of cyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA) and 4,4′-oxydianiline (ODA) for the synthesis of PI films. The obtained PIs are further crosslinked by free radical reactions using a crosslinking agent, 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TAIC) to form three crosslinked PI materials, PI-TAIC-5%, PI-TAIC-10%, and PI-TAIC-15%. The resulting all three crosslinked PI films exhibit excellent thermal properties with their glass transition temperatures (T_g) higher than 400 °C. For the mechanical properties, the formation of the rigid network structure leads to an improvement in their tensile strengths and Young's moduli. The introduction of 10 mol% TAIC in the PI (PI-TAIC-10%) shows the highest tensile strength (114.77 MPa), representing an 18.6% enhancement in comparison with that of the original PI material. In terms of dielectric properties, the crosslinking reactions effectively increase the free volumes between the polymer chains and reduce the molecular dipole moments. As a result, PI-TAIC-15% significantly reduces the dielectric properties, resulting in a decrease in the dielectric constant (D_k, from 3.42 to 3.15) and the dielectric loss (D_f, from 3.67 $\times$ 10⁻² to 2.58 $\times$ 10⁻²) under 10 GHz frequency. As far as the coefficient of thermal expansion (CTE) results, the formation of the network structure in PI-TAIC-15% restricts the movement of the polymer chains, leading to a 15% reduction in the CTE value than that of the non-crosslinked PI film. Overall, this work provides a promising strategy to optimize the mechanical and dielectric properties of high thermally stable PIs via crosslinking reactions.

聚酰亚胺(PI)因其优异的性能以及在柔性显示基板、微电子和集成电路等领域的应用而受到广泛关注。然而，交联对 PI 的热、机械和介电性能的影响仍需要进一步研究。在这项工作中，我们将含有双键的可交联单体双环[2.2.2]辛-7-烯-2,3,5,6-四甲酸二酐（BTA）引入到由环丁烷-1组成的体系中,2,3,4-四甲酸二酐 (CBDA) 和 4,4'-二苯胺 (ODA) 用于合成 PI 薄膜。使用交联剂1,3,5-三烯丙基-1,3,5-三嗪-2,4,6(1 H ,3 H ,5 H )-三酮(TAIC)通过自由基反应进一步交联获得的PI ）形成三种交联PI材料：PI-TAIC-5%、PI-TAIC-10%、PI-TAIC-15%。由此产生的所有三种交联 PI 薄膜均表现出优异的热性能，其玻璃化转变温度 ( T _g ) 高于 400 °C。对于机械性能，刚性网络结构的形成导致其拉伸强度和杨氏模量的提高。在PI中引入10 mol% TAIC（PI-TAIC-10%）显示出最高的拉伸强度（114.77 MPa），与原始PI材料相比提高了18.6%。在介电性能方面，交联反应有效地增加了聚合物链之间的自由体积并降低了分子偶极矩。结果，PI-TAIC-15% 显着降低了介电性能，导致介电常数（ D _k，从 3.42 降至 3.15）和介电损耗（D _f，从 3.67$\times$10 ^-2至 2.58$\times$10 ^-2 ) 在10 GHz频率下。就热膨胀系数（CTE）结果而言，PI-TAIC-15%中网络结构的形成限制了聚合物链的运动，导致CTE值比非TAIC降低了15%。交联PI薄膜。总的来说，这项工作提供了一种有前途的策略，通过交联反应优化高热稳定性 PI 的机械和介电性能。