Functional Siloxane Cross‐Linking Nodes in Thermoset Polymer Networks Enhance Mechanical Robustness and High‐Temperature Electrical Insulation

ABSTRACT In next‐generation power electronics and electrical systems, thermoset insulating polymers are required to simultaneously provide mechanical support and electrical insulation under extreme electrothermal conditions. However, conventional epoxy resins suffer from an inherent trade‐off between mechanical robustness and high‐temperature insulation. Herein, a nodal engineering strategy is proposed to construct multifunctional thermoset networks based on cyclic siloxane cross‐linking nodes. The siloxane nodes facilitate localized stress relaxation and homogenize the cross‐linked network, thereby enabling efficient energy dissipation while maintaining structural integrity and mechanical robustness. Meanwhile, the intensified local network constraints and homogenized chain distribution effectively decouple inter‐chain charge transport from thermally activated segmental motion. In addition, the nodal platform is further functionalized via highly efficient hydrosilylation. Fluorinated moieties are grafted onto the siloxane nodes to create localized energetic traps that suppress intra‐chain charge transport. Consequently, the resulting network simultaneously improves mechanical robustness and electrical insulation, significantly improving breakdown strength (295.09 kV mm −1 at 120°C, 92.27% increase), tensile strength (75.61 MPa, 29.85% increase), and fracture toughness (2.82 MPa m 1/2 , 57.54% increase). This study provides a new route for constructing high‐performance multifunctional polymer networks, showcasing the immense potential of functional siloxane cross‐linking nodes for high‐reliability insulation in extreme environments.