Polymer-scaffold-guided graphitization for high thermal conductivity in SWCNT-derived carbon fibers

Abstract

Carbon nanotube (CNT) fibers exhibit outstanding intrinsic properties, yet their macroscopic performance is often limited by structural disorder, void formation, and collapse during high-temperature processing. Here, we introduce a polymer-scaffold-guided graphitization strategy in which polyimide (PI) functions as a thermally stable scaffold to maintain CNT alignment, suppress collapse, and regulate structural evolution. Upon heat treatment up to 2900 degrees C, the PI-containing CNT fibers exhibited enhanced graphitic ordering, extended axial correlation length, and reduced interlayer spacing, as confirmed by Raman spectroscopy, small-angle and wideangle X-ray scattering (SAXS and WAXS). Notably, the CNT/PI fiber with 50% PI content achieved a correlation length of 13.7 nm, leading to exceptional thermal conductivity (534 + 91 W m- 1K- 1), electrical conductivity (0.64 + 0.02 MS m- 1), tensile strength (3.26 + 0.3 GPa) and modulus (870+ 138 GPa). These findings demonstrate that PI acts not only as a reinforcing polymer but also as a structural scaffold that guides graphitization and directional phonon transport, enabling the design of high-performance, anisotropic CNT-based fibers for thermal management and advanced structural applications.