Molecularly Engineered Dual-Network Polydimethylsiloxane Composites with Recoverable Thermal Transport and Low Contact Thermal Resistance

Abstract Thermal interface materials (TIMs) require both efficient heat transfer, reliable interfacial contact, and long-term damage tolerance, yet highly filled polymer composites often suffer from poor deformability, irreversible interfacial damage, and increased contact thermal resistance. Herein, a dual-network self-healing polydimethylsiloxane (SH-PDMS) matrix was designed using a dual-functional cross-linker that integrates permanent covalent cross-links with reversible Diels–Alder (DA) dynamic bonds. The permanent network provided structural stability, while the reversible DA bonds enabled thermally triggered network rearrangement and self-healing. Thermally conductive composites containing Al2O3, boron nitride, and ZnO/carbon fiber fillers were further prepared to examine how filler architecture affects self-healing behavior, recoverable thermal transport, and interfacial contact thermal resistance. Among the tested composites, ZnO/carbon fiber/SH-PDMS achieved the highest thermal conductivity of 2.5 W·m–1·K–1 owing to the formation of long-range conductive pathways and local thermal bridges. After mechanical damage, the thermal conductivity of all composites decreased substantially but recovered to more than 90% of the original value after healing, demonstrating efficient restoration of disrupted heat-transfer pathways. Notably, the thermal conductivity recovery was much higher than the corresponding mechanical recovery, indicating that heat-transfer restoration does not require complete recovery of the load-bearing network. The thermally treated SH-PDMS-based TIMs also exhibited reduced contact thermal resistance under mild pressure, with ZnO/carbon fiber/SH-PDMS reaching 0.205 K·cm2·W–1 at 70 psi. In an LED–TIM–heat sink assembly, the ZnO/carbon fiber/SH-PDMS TIM reduced the maximum LED temperature from 68.1 °C to 51.8 °C. These results demonstrate that the dual-network SH-PDMS matrix provides a promising route for self-healing TIMs with recoverable thermal transport and low contact thermal resistance.