Self-Healing High Strength and Thermal Conductivity of 3D Graphene/PDMS Composites by the Optimization of Multiple Molecular Interactions

Thermally conductive, robust, but self-healable polymer/carbon nanocomposites are the research focus in functional materials. However, the trade-off between molecular interaction and cross-linking makes it difficult to simultaneously achieve excellent self-healing, high strength, and thermal conduction. Herein, we fabricated boroxine poly(dimethylsiloxane) 2-ureido-4[1H]-pyrimidinone selectively cross-linked by molecular boron ester bonds and hydrogen bonds. By optimizing the reversible interaction, a maximum strength of 7.33 MPa and a high self-healing efficiency of 97.69 ± 0.33% were achieved at a boroxine-to-2-ureido-4[1H]-pyrimidinone molar ratio of 1:3 (BE-PDMS1:3-UPy). Highly robust composites of BE-PDMS1:3-UPy were obtained using a UPy-modified graphene aerogel. A transected sample recovered its mechanical properties (78.83 ± 2.40%) and thermal conductivity (98.27 ± 0.13%) after self-healing at 40 °C for 6 h. The outstanding reversible association/disassociation of hydrogen bonds at the polymer–graphene interface makes the composites to be used as structure–function integrated materials in interfacial thermal conductors.