“Brick–Sand–Mortar” Inspired Natural Konjac Glucomannan/BN–OH@AgNP Composite Film with High Thermal Conductivity and Electrical Insulation

Abstract The development of high-performance thermal interface materials (TIMs) that simultaneously achieve efficient thermal transport, mechanical robustness, and electrical insulation remains a major challenge. In this study, a hybrid filler system consisting of silver nanoparticle-decorated hydroxylated boron nitride (BN–OH@AgNPs) was rationally designed via in situ reduction of Ag+ ions. Inspired by a “brick–sand–mortar” architectural paradigm, a thermally conductive network was constructed in which BN–OH serves as the “bricks” forming the primary thermally conductive framework, AgNPs act as the “sand” bridging interfacial thermal resistance, and natural konjac glucomannan (KGM) functions as the “mortar” providing structural cohesion and ensuring composite integrity. The BN–OH@AgNPs/KGM composites with this integrated thermal network were fabricated by a vacuum-assisted filtration followed by a hot-pressing process. At a filler loading of 50 wt %, the resulting composite was found to exhibit a thermal conductivity as high as 12.6 W·m–1·K–1, representing a remarkable enhancement of approximately 125 times compared to the pristine KGM film. Moreover, a tensile strength of 37.6 MPa and a high volume resistivity exceeding 1010 Ω·cm were simultaneously achieved. This work provides a strategy for natural polymer-based high-performance thermally conductive insulating composites and offers a perspective for advanced TIM design.