A mechanically strong and highly thermally conductive graphene skeleton constructed by polyamide acid welding and syneresis for polydimethylsiloxane composites

Graphene skeletons have great potential for thermal management. However, their practical applications are usually limited by their low thermal conductivity (λ) due to their low density and undesirable contact efficiency between graphene nanoplatelets (GNPs). Here, a high-density, anisotropic skeleton was constructed from polyamide acid/graphene oxide/graphene nanoplatelets (PAA/GO/GNPs) hybrid dispersion by PAA welding and syneresis. Notably, the mechanical strength and thermal conductivity of the skeletons were significantly enhanced by the carbonized PAA. The internal structure of skeletons was regulated by adjusting the driving force and resistance (PAA and GNPs content) during syneresis. When the concentrations of PAA and GNP in the precursor dispersion are 20 mg/ml and 100 mg/ml, the skeleton maintains the anisotropic structure after syneresis, while its density and axial thermal conductivity (λ_axial) is 0.1701 g/cm³ and 3.104 W/(m·K). Moreover, the strength of the as-prepared skeleton is up to 1.64 MPa at 50% strain. With filling polydimethylsiloxane (PDMS) into the as-prepared skeletons, the λ_axial of the obtained thermal interface materials (TIMs) is 4.421 W/(m·K). Therefore, this work provides a facile strategy for fabricating mechanically strong and highly thermally conductive graphene skeletons as well as TIMs.