Modulating electromagnetic interference shielding performance of ultra-lightweight composite foams through shape memory function

Abstract

High-performance electromagnetic interference shielding (EMI) materials are desirable in aerospace, military and mobile electronics applications. However, fabrication of smart and ultra-lightweight EMI shielding materials with adjustable EMI shielding performance through an energy-efficient and environmental-friendly process is still challenging. Herein, we demonstrate using a conductive biomass-derived d-glucaric acid-chitosan/single-walled carbon nanotube (SWNT/GA-chitosan) polymer composite layer and a crystallized paraffin layer to fabricate ultra-lightweight polyurethane foams with shape memory and adjustable EMI shielding functions, of which the shape change via external stimulus enables the foams to adjust EMI shielding efficiency autonomously. The foam coated with synthesized conductive composite layers shows an exceptional EMI shielding effectiveness of 56 dB at an ultra-low density of 0.03 g/cm3 with only 0.171 vol% SWNT. The foam also exhibits ultra-high durability over 2000 compression-recovery cycles. Furthermore, introduction of paraffin layer as a reversible network results in shape memory foams with high fixity ratio >95% and recovery ratio >90%. These foams exhibit a wide range of adjustable EMI shielding efficiency from 18 dB to 30 dB by controlling their macroscopic shape from compression. Such smart foams with shape memory and adjustable EMI shielding functions fabricated by an environmental-friendly strategy represent a promising material candidate for the wide applications of EMI shielding.