Doping-Induced Conductivity Enhancement in Mechanically Robust and Flexible SWCNT/Conjugated-Polymer Composites for High-Performance EMI Shielding

The increasing adoption of wearable electronics has increased the demand for flexible and mechanically robust electromagnetic interference (EMI) shielding materials. However, conventional EMI shielding materials, such as metals and MXenes, are limited by flexibility, stability, and processability. To address these challenges, we developed a composite platform comprising single-walled carbon nanotubes (SWCNTs) and electron-donating conjugated polymers (CPs). The electrical conductivity and EMI shielding effectiveness (EMI SE) of the resulting composites increased proportionally with the doping efficiency of the CPs. AuCl₃-doped SWCNT/CPs with a thickness of 21 µ m exhibited a conductivity exceeding 5000 S/cm and an EMI SE of 78 dB, comparable to that of Ti₃C₂Tₓ MXene, one of the most effective inorganic EMI shielding material. A 50 wt.% SWCNT composition in SWCNT/CP composites formed a sheath–core fiber network with outstanding mechanical properties (Young’s modulus: 12.10 GPa; tensile strength: 82.59 MPa) while maintaining its EMI SE even after 300,000 folding–unfolding cycles. Although a molecular dopant (2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane, F4TCNQ) led to a slightly lower conductivity than a Lewis acid dopant (AuCl₃), it resulted in higher EMI absorption at comparable conductivity levels due to increased radical generation, as confirmed by electron spin resonance and permittivity analysis. These findings highlight the critical role of dopant selection and CP design, positioning SWCNT/CP composites as a promising platform for next-generation EMI shielding materials.