Double-Layer Architecture for Improving Mechanical and Dielectric Properties in Low-Dielectric Porous Polyimide Composites

The high dielectric constant inherent to traditional polyimides (PIs) limits their ability to meet the demands of high-frequency circuit boards. The challenge of reducing this dielectric constant, while simultaneously preserving or enhancing the material's overall performance, is of critical theoretical and practical significance for advancing the use of PIs in the 5G communication sector. In this study, fluorinated graphene/polyimide (FG/PI) was employed as a reinforcing layer to fabricate a double-layer structure that enhances the mechanical and breakdown properties of low-dielectric PIs. PI porous composite films were developed using a layer-by-layer coating method, and their dielectric, mechanical, and thermal properties were investigated. The resulting double-layer PI films exhibited low dielectric constants and robust comprehensive performance. Specifically, the dielectric constants of the three films, PI-1, PI-2, and PI-3, were 2.01, 1.90, and 1.70, respectively, with corresponding tensile strengths of 42.69 MPa, 37.54 MPa, and 24.41 MPa, and breakdown strengths of 180.75 kV mm⁻¹, 138.70 kV mm⁻¹, and 89.77 kV mm⁻¹. These results underscore the importance of multi-layer structural designs in enhancing the breakdown resistance and mechanical properties of porous films, which are critical for the practical application of low-dielectric porous PI materials.