Delamination-Free Multifunctional Composite via Sugar-Templating for Thermal Interface Materials with Electromagnetic Interference Shielding and Electrical Insulation

Multifunctional thermal interface materials (TIMs) that simultaneously provide efficient heat dissipation, strong electromagnetic interference (EMI) shielding, and reliable electrical insulation are highly desirable for flexible and high-power electronic devices. However, their long-term reliability is often compromised by interfacial delamination, a critical yet insufficiently addressed challenge in multilayer architectures. Herein, a scalable strategy for fabricating a delamination-free sandwich-structured boron nitride (BN)/graphene nanoplatelets (GNP)/polydimethylsiloxane (PDMS) composite via sugar templating, followed by layer-by-layer casting and vacuum infiltration. The porous BN/PDMS and GNP/PDMS layers facilitate the formation of a mechanical interlocking (MIL) architecture at the interfaces, as PDMS infiltrates and solidifies within the interconnected pore network. This results in strong interlayer adhesion without the need for surface functionalization or hot pressing. The optimized MIL composite (M-BN25/GNP30) exhibits a total EMI shielding effectiveness of 34 dB in the X-band, a through-plane thermal conductivity of 1.10 W·m–1·K–1, and a volume resistivity of 2.35 × 1013 Ω·cm. Compared with its nonmechanical interlocking (NMIL) counterpart (N-BN25/GNP30), the MIL structure delivers approximately 21.43% higher EMI shielding effectiveness, ∼46.67% higher thermal conductivity, and ∼45.01% greater interfacial shear strength. Moreover, the MIL composite retains its mechanical integrity and functional performance even after 10,000 bending cycles and 1000 thermal cycles (−20 to 120 °C), with no observable delamination. These results demonstrate that the MIL sandwich architecture provides a robust, scalable approach for developing multifunctional, delamination-free, durable TIMs for flexible and high-power electronic applications.