Doping-engineered SWCNT/polymer networks for mechanically robust and highly flexible broadband EMI shielding

Abstract

Broadband electromagnetic interference (EMI) shielding materials that combine high electrical conductivity with mechanical flexibility and robustness are increasingly needed for wearable and miniaturized electronics. Here, we present doping-engineered composites based on single-walled carbon nanotubes (SWCNTs) and electron-donating conjugated polymers (CPs) that simultaneously achieve high electrical conductivity, strong EMI shielding effectiveness, and excellent mechanical durability. Systematic comparison of molecular (F4TCNQ) and Lewis acid (AuCl3) dopants reveals that both electrical conductivity and EMI shielding performance are governed by doping efficiency and dopant-dependent charge-generation mechanisms. An optimized composite containing 50 wt% SWCNT forms a robust fibrous conductive network, exhibiting conductivity above 5000 S cm−1, high mechanical strength (Young's modulus >13 GPa, tensile strength >96 MPa), and EMI shielding effectiveness exceeding 75 dB in the X-band and 90 dB up to 110 GHz, while maintaining performance after 300,000 folding cycles at a 3 mm bending radius. Conductivity-matched comparisons further show that dopant engineering strongly influences dielectric loss and absorption behavior, highlighting dopant selection as a key design parameter for simultaneously optimizing electrical conductivity, dielectric loss, and mechanical robustness in flexible SWCNT/CP-based EMI shielding materials.