Thermally and electrically anisotropic silicone rubber composites with frequency-selective EMI shielding

The rapid development of highly integrated and multifunctional electronic devices urgently requires polymer composites with anisotropic thermal and electrical conductivities and electromagnetic interference (EMI) shielding. Herein, the precise control of high alignment and alternating distribution of graphite (Gt)-carbon nanotubes (CNTs) and hexagonal boron nitride (h-BN) via co-extrusion to fabricate alternating multilayered SR composites were reported. Such ordered hierarchical structures not only constructed efficient thermally and electrically conductive networks within the layer but also effectively segregated the electrical and thermal conduction path in the through-plane direction. Simultaneously, owing to the destructive interference of EM waves between the two Gt-CNTs layers, resulting in significant improvements in total shielding effectiveness along with obvious shielding peak shift with decreasing the thickness of the h-BN layer. The 4-layer SR composites exhibited anisotropic thermal and electrical conductivities and frequency-selective EMI Shielding. Specifically, the 4-layer SR composites exhibited in-plane thermal conductivity of 8.71 W/mK, breakdown voltage of 8.0 kV/mm and EMI shielding effectiveness of 31-43.2 dB, when the thickness ratio of the Gt-CNTs layer and the h-BN layer was 4:1. Furthermore, the ordered hierarchical structures of the SR composites could be directionally transformed through stacking-cutting to meet different heat dissipation and electrical conduction application scenarios. This research provides new insights into the simple preparation, rational design and multifunctional integration of polymer composites for advanced electronic devices.