Simultaneous improvement in dielectric, water resistance and mechanical properties of polyimide (PI) films is critical for their practical use, but difficult to achieve. Herein, a sandwich‐type porous GO/PI film with excellent comprehensive properties was obtained through integrating a GO‐containing complex, fluorine‐containing porous structure and sandwich‐type distribution of porous structure by a simple, low‐cost and green breath figure method. With the addition of only a small amount of GO‐containing complex, a low dielectric constant of 2.21, water absorption of 0.51%, increment in dielectric constant after moisture treatment of 1.60% and high tensile strength of 113.1 MPa, tensile modulus of 1.70 GPa, with 35.39%, 79.42%, 81.81% of reduction and 17.22%, 21.43% of increase compared to PI film were shown, respectively. Moreover, these properties could be adjusted through regulating the component and porous structure by changing the parameters of breath figure method. These outstanding properties make the film a promising candidate for high‐performance low‐dielectric materials.

The dimensional and property stability after heating is considered to be one of the most important properties for low-dielectric-constant materials. Herein, porous structure contained composite PI film with porous PI structure on the surface of a flat PI film was prepared through the simple and low-cost microemulsion method. The introduction of porous coating can significantly improve

The dielectric and other properties of low‐dielectric‐constant materials after heating are crucial to their performance and use, but rarely studied. In this article, sandwich‐type porous polyimide (PI) film in which porous structures located on both upper and lower surfaces of flat PI film was prepared through the simple, low‐cost and green microemulsion method. The porous structures were preserved after heating due to the usage of thermally stable fluorine‐contained PI (FPI) and PI as skeleton and substrate of the porous structure, respectively, but with the increase of pore size because of the removal of thermally unstable surfactant on the inner surface of the pores. More importantly, 2.89%–5.57% of reductions in the dielectric constant with the maintenance of low dielectric loss and water absorption and high mechanical strength were observed after heating. Therefore, the low dielectric properties of heated films were well preserved upon high humidity treatment. Moreover, the structure and properties of the heated films could be adjusted via controlling the parameters in the microemuslion method. These excellent properties after the high‐temperature treatment facilitate the application of the sandwich‐type porous PI film as dielectric materials in high‐temperature environment.