Chemical structure and properties of high frequency low dielectric high temperature resistant polyimide composites

To address the urgent demand for polyimide (PI) composites with low dielectric properties, high temperature resistance and high mechanical strength in 5G high-frequency communication and hypersonic vehicles, this study proposes a molecular structure design strategy based on anhydride configuration regulation. Polyimide resins and composites are prepared using fluorinated diamine 4, 4’-diamino-2, 2’-bis(trifluoromethyl) biphenyl (TFMB) and anhydrides with distinct configurations. The regulatory mechanisms of anhydride monomer configurations on the dielectric response, thermal stability and mechanical strength of materials are systematically investigated. The results show that ―CF₃ groups in 4, 4’-(hexafluoroisopropylidene) diphthalic anhydride (6FDA) significantly reduce the dielectric constant and dielectric loss of composite materials in the X-band (8.2-12.4 GHz) by lowering the surface energy and molar polarizability. In contrast, the symmetric rigid frameworks of 3, 3’, 4, 4’-benzophenonetetracarboxylic dianhydride (BTDA) and 3, 3’, 4, 4’-biphenyltetracarboxylic dianhydride (s-BPDA) significantly enhance thermal stability, yielding a glass transition temperature (T_g) exceeding 470 ℃ for the composites. Copolymerization of structurally diverse anhydrides lowers curing temperature while imparting composites with excellent high-frequency low-dielectric properties and thermal resistance.Building on these findings, a configuration complementary strategy involving copolymerization of 6FDA and BTDA synergistically achieves high-frequency low-dielectric characteristics as well as collaborative optimization of a 24 ℃ reduction in curing temperature and an increased flexural strength of 442.8 MPa.