One-Step in Situ Ball Milling Synthesis of Polymer-Functionalized Few-Layered Boron Nitride and Its Application in High Thermally Conductive Cellulose Composites

The chemically inert surface and strong ionic bonds make exfoliation and functionalization of hexagonal boron nitride (h-BN) difficult. This inevitably increases the interface thermal resistance and hinders phonon transfer. Herein, polydopamine (PDA)-coated exfoliated h-BN, denoted as exfoliated h-BN@PDA, was prepared by a one-step ball milling route. During the ball milling process, dopamine self-polymerized into PDA on the surface of the exfoliated h-BN@PDA in an alkaline aqueous solution. The coated PDA contents were estimated to be about 3 wt %. Meanwhile, exfoliation of h-BN occurred due to the hydrolysis of h-BN in water and the shear force introduced by ball milling. The results reveal that the exfoliated h-BN generally composed of <20 layers. The resulting exfoliated h-BN@PDA was further added to cellulose nanocrystal (CNC) and improved thermal conductivity up to 40 W m^-1 K^-1 with 94 wt % h-BN. By controlling the feed ratio, exfoliated h-BN@PDA/CNC composites with different h-BN contents were fabricated. The corresponding thermal conductivity increased with increasing h-BN contents. A facile, highly efficient, and moderate route to prepare modified few-layered two-dimensional layered materials was provided. These composites have great potential in thermal management applications.