Influence of Flexible Aromatic Ether Diamine Structures on Aggregation State and High-Frequency Dielectric Properties of Polyimide Films

With the growing demand for high-speed, high-capacity transmissions, materials with ultralow dielectric loss (Df) and low dielectric constant (Dk) are crucial. Polyimides (PIs) are widely used because of their excellent thermal stability and mechanical properties. However, their relatively high dielectric losses at high frequencies limit their application. In this study, four PIs were designed and synthesized using a rigid 4,4′-p-terphenyltetracarboxylic dianhydride (TPDA). The aggregation-state structure of the polyimides is regulated by the introduction of diamines with different flexible structures. The synthesized polyimide film TPDA-aODA exhibits excellent overall properties with a Df of 0.0023, a Dk of 3.34 (RH @ 50%), and a tensile elongation of 96%. The aggregation state structure of the films was confirmed using WXRD, POM, and DSC characterization techniques, and the effects of different flexible diamines on the aggregation state structure and high-frequency dielectric properties of the polyimide films were investigated. The experimental results indicate that the structure of the aggregation state of the polyimide films significantly affects their dielectric properties. These findings provide insights into the design of low-Df polyimide materials.