Aminophenyl polyhedral oligomeric silsesquioxane crosslinked polyimide films: Functionality-driven design for low dielectric constant, enhanced mechanical performance, and high thermal stability

Aminophenyl-functionalized polyhedral oligomeric silsesquioxanes (POSS), as organic-inorganic hybrid nanostructures with tunable functionalities, show significant potential for tailoring the properties of polyimide (PI) films. Here, we synthesized aminophenyl POSS derivatives with different amino functionalities through a newly developed, efficient, and metal-free reduction strategy, and subsequently constructed a series of PI film systems, including a linear non-crosslinked control, a 1,3,5-tris(4-aminophenoxy)benzene (TAB)-crosslinked reference, and POSS-crosslinked networks of varying functionalities. The functionality-dependent influence of POSS on network topology and PI film properties was systematically investigated. Low amino-functionality POSS (PI-3NH₂-OPS) imparted superior dielectric insulation (ε = 2.44, tan δ = 0.0024 at 10 MHz), high flame retardancy (LOI = 58.6%), and excellent moisture resistance. Medium amino-functionality POSS (PI-5NH₂-OPS) optimized mechanical performance, achieving a tensile strength of 139.06 MPa and modulus of 8.61 GPa, while high amino-functionality POSS (PI-OAPS) enhanced thermal stability (Tg = 308.9 °C), reduced CTE by 30.7%, and maintained optical transparency. Based on these results, we propose a “functionality-performance-application” ternary mapping model that establishes predictive correlations between POSS structural parameters, PI film performance, and targeted application requirements. This work provides mechanistic insights and a rational design strategy for multifunctional PI films in high-frequency electronics, flexible devices, and high-temperature packaging.