Despite their promising application prospects in electromagnetic interference (EMI) shielding, a significant challenge remains in endowing flexible porous polymer-based conductive composites with exceptional thermal management capabilities. In this study, PDMS/GNPs foam serves as a three-dimensional (3D) porous skeleton, with LM nanoparticles anchored on its surface, creating a poly(dimethylsiloxane)/graphene nanoplatelets@liquid metal (PDMS/GNPs@LM) composite foam with a dual network structure, achieved through a simplified salt template and extrusion impregnation method. Owing to the successful construction of this dual 3D network structure, when the filler loading is 22.34 vol%, PDMS/GNPs@LM foam exhibits an excellent thermal conductivity of 0.74 W m−1 K−1, representing a 1133% enhancement compared to the neat PDMS foam. Finite element simulations demonstrate that the LM layer network exhibits excellent heat transmission due to the effective adhesion of adjacent LM nanoparticles via the polyvinyl alcohol adhesives, with heat flux mainly transferred through the continuous LM framework. The PDMS/GNPs@LM foam possesses an outstanding electrical conductivity of 35.15 S m−1 and excellent EMI shielding effectiveness of 40.8 dB (with a thickness of only 2.13 mm). Furthermore, the PDMS/GNPs@LM foams demonstrate good mechanical flexibility and exhibit rapid electrothermal response and hydrophobicity. Based on these merits, the PDMS/GNPs@LM foam is anticipated to find applications in electronics, particularly in intelligent electromagnetic protection and thermal management systems.
Electromagnetic interference (EMI) shielding materials with absorption-dominated EMI shielding mechanism can effectively annihilate electromagnetic waves (EMW) and avoid their repeated EMW pollution. However, it is difficult to achieve this goal for conductive polymer-based composites (CPC), because the interface impedance mismatch between air and CPC leads to massive reflection of EMW at the interface. Pores are beneficial to EMW penetrating into the interior of CPC and causing their multiple reflection, scattering and absorption in pores, thus endowing CPC with absorption-dominated EMI shielding characteristic. Herein, highly conductive silvered aramid microfibers (CAMF) were first synthesized via dopamine-assisted electroless deposition of silver coating on aramid microfibers (AMF), and then the conductive porous PDMS composite foams (PDMSF) with absorption-dominated EMI shielding characteristic were prepared and optimized via salt template method. As a result, PDMSF with 1.7 vol% silver content, the conductivity of PDMSF can reach 10 -1 S/m, the EMI shielding efficiency (EMI SE) can reach 36.7 dB in X-band, and the average absorption ratio in EMI SE is 87%, while the density of PDMSF is only 0.28 g/cm 3 . The combination of lightweight, high EMI SE and absorption-dominated EMI shielding characteristic makes the porous PDMSF the latent EMI shielding materials in special constructions (e.g. military, confidential and nuclear facilities, etc.), aerospace, military equipments and transportation, etc.
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