Synergistically Enhanced Properties of Polyimide Films via In-Situ Hollow SiO₂ Nanospheres

Polyimide (PI) films serving as high-temperature dielectric and structural materials are increasingly required to combine mechanical robustness, thermal stability, and low dielectric properties for advanced electronic packaging. Herein, PI composite films incorporated with 110 nm hollow SiO₂ nanospheres were fabricated via in-situ synthesis and subsequent thermal imidization. The optimal comprehensive performance was achieved at a SiO₂ filler loading of 10%. Relative to pristine PI, the optimal composite delivered a 33% enhancement in room-temperature tensile strength (reaching 68 MPa), a 28% increase at 200 °C (reaching 64 MPa), and a 64% improvement at 250 °C (reaching 66 MPa). Benefiting from the hollow filler structure, this sample also exhibited enhanced ductility (reflected by a 1.3% rise in elongation at break), the most favorable thermal stability among all specimens, and a 3.5% reduction in relative dielectric constant, collectively achieving the synergistic enhancement of mechanical, thermal, and dielectric properties and rendering the composite a promising candidate for high-temperature electronic insulation applications.