Engineering designed functional covalent organic frameworks via pore surface modifications for effectively reducing the dielectric constant of polyimide-based electronic packaging materials

Polyimide (PI) is considered one of the most promising candidate materials for the microelectronics and wireless communication industries. Nevertheless, the relatively high dielectric constant of PI has become a significant obstacle, constraining its utilization in the realm of microelectronics. Herein, novel PI nanocomposite films were fabricated by incorporating covalent organic frameworks (COFs) and their functionalized counterparts (COF@POSS and COF@DTF) through post-synthetic modification. Among all PI nanocomposites films, PI/ COF@POSS nanocomposite film including 2 wt% COF@POSS achieved the lowest dielectric constant (2.41) and dielectric loss (0.0076). These values represented a reduction of 22.5 % and 24 % compared to pure PI, respectively. The decrease in dielectric constant is ascribed to the combined influence of the porous structure of COF and the augmentation in free volume fraction caused by the steric hindrance of POSS. Additionally, the tensile strength of the PI/COF@POSS and PI/COF@DTF nanocomposite films increased up to 121.1 MPa and 112.0 MPa, representing a 95% and 80% improvement over pure PI, respectively. Furthermore, the introduction of COFs functionalized with POSS and DTF significantly enhanced the hydrophobicity of PI nanocomposite films. The combination of porous organic nanofillers with surface functionalization offers a feasible route to create lowk PI nanocomposite films with improved mechanical properties and hydrophobicity.