An effective design strategy for preparing highly transparent polyimide film with low dielectric constant is presented. The key to the strategy is to simultaneously introduce meta-substituted structure and trifluoromethyl in polymer chains. By using this design strategy, a highly transparent polyimide film with low-k was synthesized from 3,5-diaminobenzotrifluoride (m-TFPDA) and 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) through a two-step method. The obtained m-TFPDA/6FDA (CPI) film (∼30 µm) possesses high optical transparency (λ_cutoff=334 nm, T_450nm=85.26%, Haze=0.31) and is close to colorless (L*=96.03, a*=−0.34, b*=2.12, yellow index=3.96). The intrinsic k and dielectric loss value of the film are 2.27 and 0.0013 at 10 kHz, respectively. More importantly, such low dielectric performance could remain stable up to 280 °C, and the film shows a low moisture rate (∼0.51%), which helps to maintain the low-k property stability in different humid environments. Meanwhile, the film also shows good thermal stability and mechanical properties, with a glass transition temperature (T_g) of 296 °C and the 5 wt% decomposition temperature (T_d,5%) of 522 °C under N₂. The tensile strength and tensile modulus of the film are 85.1 MPa and 1.96 GPa, respectively. In addition, the film is soluble in common solvents, which allows simple solution processing and low-cost, continuous roll-to-roll processes. This design strategy is beneficial to improving the transparency, lightening yellow color, lowering the dielectric constant and meanwhile maintaining the comprehensive properties of polyimide films, which is mainly due to the introduced meta-substituted and trifluoromethyl structures effectively inhibiting the transfer of charge transfer complex (CTC) effects and increasing the free volume of film. This design strategy could also be extended to other high-performance polymer systems.

提出了一种制备低介电常数的高透明聚酰亚胺薄膜的有效设计策略。该策略的关键是在聚合物链中同时引入间位取代的结构和三氟甲基。通过这种设计策略，通过两步法，由3,5-二氨基苯并三氟化物（m -TFPDA）和4,4'-（六氟异亚丙基）二邻苯二甲酸酐（6FDA）合成了具有低k的高透明聚酰亚胺薄膜。所得的m -TFPDA / 6FDA（CPI）膜（〜30 µm）具有高的光学透明性（λ_截止= 334 nm，T _450nm = 85.26％，雾度= 0.31），接近无色（L * = 96.03，a）。* =-0.34，b * = 2.12，黄色指数= 3.96）。薄膜的本征k和介电损耗值在10 kHz时分别为2.27和0.0013。更重要的是，这种低介电性能可以在高达280°C的温度下保持稳定，并且薄膜显示出较低的水分率（〜0.51％），这有助于在不同的潮湿环境中保持低k性能的稳定性。同时，该膜还显示出良好的热稳定性和机械性能，在N ₂下具有296°C的玻璃化转变温度（T _g）和522°C的5 wt％分解温度（T _d，5％）。。膜的拉伸强度和拉伸模量分别为85.1MPa和1.96GPa。另外，该膜可溶于普通溶剂，这使得溶液加工简单并且成本低廉，连续的卷对卷工艺成为可能。这种设计策略有利于提高透明度，淡黄色，降低介电常数并同时保持聚酰亚胺薄膜的综合性能，这主要是由于引入的间位取代和三氟甲基结构有效抑制了电荷转移复合物的转移（ CTC）效果并增加胶卷的自由体积。该设计策略也可以扩展到其他高性能聚合物系统。