Single-Walled Carbon Nanotube Polyelectrolytes with a Coherent Skin Effect for Electromagnetic Interference Shielding

Compartmental shielding, using methods such as the conductive encapsulation of flexible polymer fibers, provides electrical pathways that are effective for electromagnetic interference (EMI) shielding in textile-based EMI shields. However, controlling the skin depth with electrically insulating polymer constituents remains challenging, particularly by requiring the high electrical conductivity of the encapsulants on the surface. Here, we demonstrate that the highly conductive single-walled carbon nanotube (SWCNT) polyelectrolytes provide a certain level of electrical conductivity (∼10⁶ S/m) with effective percolation that reduces the skin depth to approximately 3 μm. This experimental skin depth was well-matched with the theoretical value of the skin depth. Sufficient charge accumulation in the SWCNT encapsulants with a hierarchical structure indicates the remarkable conductive features of the SWCNT polyelectrolytes and successfully demonstrates absorption-dominant EMI shielding. The macroscopic square mesh consisted of core/shell aramid/SWCNT fibers, exhibiting an ordered structure across multiple length scales, a modified hierarchy, and a superior EMI shielding effectiveness (SE), particularly in absorption. In particular, an EMI SE (i.e., 32 dB) of approximately 99.9% was achieved using a square mesh with an aperture width of 3 mm. The square meshes demonstrated excellent flexibility, thermal stability (T_d > 500 °C), and mechanical robustness (σ = 2.26 ± 0.16 GPa, E = 79.0 ± 1.8 GPa, and ε = 2.99 ± 0.09%).