pH‐Tunable 3D Interconnected Network of Multiwalled Carbon Nanotubes /Polyacrylic Acid Hydrogel with Excellent Electromagnetic Radiation Shielding Capability

Abstract The fabrication of durable and high anticorrosion hydrogel composite materials composed of multi‐walled carbon nanotubes (MCNTs) and crosslinked polyacrylic acid (PAA) for EMI shielding application is reported. The MCNTs contribute to the generation of 3D porous structures and enhance the mechanical properties of composite hydrogel. The 3D porous structure and high electrical conductivity inherited from ultrahigh electrically conductive MCNTs enable excellent EMI shielding properties with a total shielding efficiency EMI SE (SE_T) value of 32.8 dB (>99.9%) at only 3 wt% filler content of MCNTs. The MCNTs/PAA hydrogels also display superior EMI shielding performance under a strong acidic environment with SE_T > 99.99% while the 3D porous structure remained intact. The combination of electron–ion system in pH solution enriches the charge transfer and accumulation, enabling dipole orientation and polarization that are favorable for enhancing EMI attenuation. Moreover, the porous structure of MCNTs/PAA also contributes to partial trapping and dissipation of EM radiation energy via multiple scattering phenomena. This work thus paves the way toward applications of 3D hierarchical network materials for EMI shielding applications in both land and aqueous environments.