Surface and Interfacial Engineering of Functionalized Nanofillers in COC Matrix for Flexible Ultra-Low-κ Composites

The advancement of next-generation electronics necessitates dielectric materials that simultaneously achieve ultralow dielectric constants (Dk), high thermal stability, mechanical robustness, and flexibility. While traditional polymers such as polytetrafluoroethylene, polyimide, and epoxy resins offer partial solutions, their limitations including high Dk values, brittleness, and thermal instability hinder their applicability in emerging technologies such as 5G networks and flexible electronics. This study introduces a multifunctional cyclic olefin copolymer (COC)-based composite engineered to address these challenges through the integration of functionalized boron nitride nanosheets (BNNs), SiO2 nanoparticles, and a polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) triblock copolymer. BNNs and SiO2 were functionalized with cetyltrimethylammonium bromide (CTAB) to improve filler dispersion within the COC matrix. The study compares three formulations: pure COC, COC-BNNS-SEBS, and COC-BNNS-SiO2-SEBS. Dielectric properties were measured over a frequency range of 8.2–12.4 GHz, with the composites achieving optimal dielectric constants of 1.61 and 1.72 @ 10 GHz and minimum loss (δ) of ∼0.0001085 and ∼0.0001612, alongside a dielectric breakdown strength exceeding 96.7 kV/mm, high thermal conductivity (up to 1.17 W·m–1·K–1), and improved mechanical strength and flexibility. These results underscore the potential of these composites for high-frequency applications requiring tailored dielectric properties and robust performance.