Hyperbranched Polysiloxane-Enhanced Silicone Elastomer Composites for Balanced Thermal Conductivity and Mechanical Properties in Thermal Interface Materials

High-power electronic devices require thermal interface materials (TIMs) with exceptional thermal conductivity and mechanical durability. However, traditional polymer composite systems often sacrifice one of these properties to enhance the other. In this study, we introduce a nanoengineered hyperbranched polysiloxane (HPSi) modified silicone elastomer composite that overcomes this trade-off challenge through a hyperbranched cross-linker-mediated multilevel cross-linked network. The HPSi-Vi with a gradient vinyl content, synthesized via controlled hydrolysis–condensation reactions, is incorporated into a poly(methylvinylsiloxane) matrix. While increasing the cross-linking density of the elastomer, HPSi-Vi effectively suppresses the agglomeration behavior of inorganic fillers, enhances the interaction between the elastomer and fillers, and reduces interfacial thermal resistance ( R c ). The optimized composite exhibits a high through-plane thermal conductivity of 1.51 W·m –1 ·K –1, which is a 505% improvement compared to pure silicone elastomer, while also demonstrating a tensile strength of 6.4 MPa, a tear strength of 20.6 kN·m –1, and a volume resistivity of 0.52 × 10 15 Ω·cm. Therefore, this composite system possesses excellent thermal conductivity, mechanical strength, and electrical insulation properties. This work provides a scalable strategy for developing high-performance TIMs with integrated functionalities, contributing to advanced thermal management in next-generation electronic products.