Cobalt-modified graphene nanosheets/cellulose thermally conductive composite films fabricated via layer-by-layer self-assembly approach

As the integration of electronic devices continues to increase, the heat generated by electronic components presents significant thermal management challenges. Thermal interface materials thus play more and more crucial role in ensuring the reliability of electronic devices. Cobalt nanoparticles (Co) were first coated onto the surface of graphene nanosheets (GNS) and grafted with maleimide (MI) to form Co@MI-GNS filler. This filler was then evenly dispersed in a carboxylated nanocellulose (CNF) matrix, and a series of Co@MI-GNS/CNF thermally conductive composite films were successfully fabricated using a layer-by-layer (LBL) self-assembly method. During the preparation process, the “C-N-C” covalent bonds were in-situ formed, enhancing the establishment of stable hydrogen bonds between the fillers and the matrix. As compared to other fabrication methods, such as blade coating or template drying, the Co@MI-GNS/CNF films produced by this approach indeed exhibited superior thermal conductivity (TC). The interfacial thermal resistance of the composite films was obtained as 9.41×10 -10   m²·K·W -1 using the Foygel model, indicating a significant improvement on the thermal transfer efficiency. Theoretical predictions were found to be consistent with thermal dissipation tests conducted on light emitting diode and computer central processing unit. The LBL self assembly proved to be a promising technique for fabricating polymer-based TIMs with ultra-high in-plane TC as well as excellent mechanical flexibility, making it particularly suitable for flexible electronic devices.