Dual-Functional Star-Shaped Polysiloxanes Enhance Thermal Interface Materials by Suppressing Oil Bleeding and Reducing Thermal Resistance

With the miniaturization and high integration of modern electronic devices, thermal interface materials (TIMs) with high thermal conductivity and long-term reliability are urgently required. This study proposes a molecular engineering strategy employing star-shaped polysiloxane derivatives to address the critical trade-off between thermal performance, processability, and reliability in silicone-based TIMs. Vinyl-terminated star-shaped polymers (Q-m-Vi) are introduced into the poly(dimethylsiloxane) (PDMS) matrix to modulate the cross-link network topology. Optimizing the degree of polymerization (DP = 40) and the dosage of Q-m-Vi facilitates the formation of a uniform, dense three-dimensional network. This architecture effectively immobilizes free silicone chains, significantly suppressing the “oil bleeding” phenomenon while maintaining matrix compliance to ensure low contact thermal resistance. Concurrently, alkoxy-terminated star-shaped polymers (Q-m-OMe) are utilized for surface treatment of AlN/Al 2 O 3 hybrid fillers. Q-m-OMe forms robust covalent bonds (Si–O–Al) and a dense organic coating on filler surfaces, drastically enhancing interfacial compatibility. Molecular dynamics simulations confirm that Q-m-OMe constructs an effective phonon bridge via low-frequency resonance and high-frequency extension, minimizing interfacial phonon scattering. By further optimizing the filler formulation (78 vol % loading with a 6:3:3 volume ratio of 120 μm AlN: 10 μm Al 2 O 3: 1 μm AlN), the fabricated thermal pad achieves an excellent thermal conductivity of 3.67 W·m –1 ·K –1 and a low thermal resistance of 8.29 K·cm 2 ·W 1– . This work demonstrates a dual-functional modification approach using tailored star-shaped polymers, offering a promising pathway to the development of next-generation high-performance TIMs.