Lightweight and self‐healing thermally expandable microsphere/silver composites with segregated conductive network for high‐efficiency electromagnetic interference shielding

Abstract Polymer‐based electromagnetic interference (EMI) shielding materials with lightweight, self‐healing and high shielding performance show a wide application in electronics, medicine, national defense, aerospace and other fields. However, the conflict between a good conductive network structure and obtaining low density and excellent self‐healing property brings about tremendous challenges for fabricating these polymer‐based materials. Herein, a lightweight and self‐healing thermally expandable microsphere / silver (TEM/Ag) EMI shielding composites were prepared through a thermal foaming process. Due to the segregated Ag conductive network and expanded porous microsphere structure, the TEM/Ag composites possessed low density (0.095 g/cm3) and super‐high EMI specific shielding effectiveness (2816.3 dB cm2/g). In addition, benefiting from this unique structure, the composites exhibited excellent EMI shielding durability that can withstand ultrasonic washing 6 h (100 W), ethanol (99.5% purity), strong acid (pH 2.0), strong base (pH 12.0), NaCl solution soaking and long‐term air exposure (180 days). Furthermore, the inherent long‐chain entanglement imparts the composites a self‐healing feature, and 86% of the EMI shielding effectiveness can be maintained after self‐healing procedure.