Ultra-low-permittivity, high hydrophobic, and excellent thermally stable fluoroelastomer/polyimide composite films employing dielectric reduction

• The organic filler fluoroelastomers were introduced into polyimide, which realized controllable preparation of ultra-low permittivity ( ε =1.21) all-organic polyimide composite films for the first time. • The FEM/PI composite films exhibited excellent thermal stability, outstanding mechanical properties and high hydrophobicity. • The preparation process of FEM/PI composite films is simple and the developed films presented excellent practical application potential. Dielectric materials with low permittivity are urgently needed in the field of microelectronics due to the development of integration and miniaturization of integrated circuits. In this work, a series of all-organic polyimide (PI) films with ultra-low-permittivity and high hydrophobicity were successfully synthesized by introducing a kind of fluoroelastomer (FEM). And the significant permittivity reduction phenomenon was discussed through molecular dynamics simulations and practical tests. It was assumed that the hydrogen bond significantly inhibited the dipolar polarization of the FEM/PI composite system, which played an important role in determining the dielectric properties of FEM/PI composite films. At a low filler content of 7 wt%, FEM/PI composites exhibited the optimum permittivity ( ε ) of 1.21 at 10 6 Hz, which was the lowest permittivity of the PI films, while a low water absorption of 0.44% and high thermal stability with a 5 % decomposition temperature ( T d5% ) of 554 o C were also observed. This simple and effective strategy of fabricating ultra-low-permittivity PI film is a potential way to realize commercial process.