Highly conductive and mechanically strong metal-free carbon nanotube composite fibers with self-doped polyaniline

Individual carbon nanotubes (CNTs) have gained popularity as lightweight wire materials due to their high electrical conductivity and low density than that of copper wires. Despite intensive research on light-weight and highly conductive CNT fibers, the bulk properties of CNT assemblies are inferior to those of metal wires in terms of electrical conductivity. Herein, we propose a method to increase the specific electrical conductivity of CNT fibers with polyaniline (PANI). The structure and physical properties of the CNT fibers are precisely controlled by optimizing the PANI content through a simple and effective solution process. PANI is considered to enhance CNT orientation, decrease voids, and dope the CNT fibers, resulting in a better electron flow in the fibers. The developed composite fiber with 5 wt% PANI demonstrated remarkable specific electrical conductivity of 6,200 ± 160 S m²/kg (11.9 MS/m) (max: 6,360 S m²/kg), an improvement of 16% above as-spun CNT fiber. Simultaneously, the mechanical properties increased by 27%, yielding a high specific tensile strength of 2.63 ± 0.10 N/tex (5.05 GPa). Furthermore, the toughness improved to 79.5 J/g, approximately a 1.8 times improvement over that of the CNT fiber. The addition of a small amount of PANI to CNT fibers has led to significant improvements in electrical and mechanical properties, which can provide insights into research on the CNT fiber field.