Hydrogen-bonding strategy helps carbon nanotube fibers become stronger and tougher

Carbon nanotubes are widely seen as ideal building blocks for advanced fibers because of their exceptional intrinsic mechanical, electrical, and thermal properties. But translating those nanoscale advantages into macroscopic fibers has remained difficult. In real carbon nanotube fibers, assembly defects, incomplete alignment, internal voids, and weak interactions between nanotubes can all limit stress transfer, causing nanotubes or bundles to slip before the network can fully bear the load. Even wet-spun fibers, which can achieve relatively good alignment and structural uniformity, still face persistent void formation during coagulation and solvent exchange.

To address this challenge, a research team from Beijing Graphene Institute, Peking University, Suzhou Institute of Nano-Tech and Nano-Bionics of the Chinese Academy of Sciences, and collaborating institutes developed a wet-spinning strategy based on reinforcing intertube interactions with poly(p-phenylene-2,6-benzobisoxazole) nanofibers and chains, abbreviated as PBOs. The resulting PBO/carbon nanotube composite fibers are referred to as PCNTFs. The study was published in Nano Research.

The researchers first functionalized carbon nanotubes so that hydroxyl-containing groups were introduced onto the nanotube sidewalls. These functionalized nanotubes were then combined with PBOs in a chlorosulfonic-acid-based liquid-crystalline spinning dope. During fiber formation, oxygen and nitrogen atoms in PBOs formed hydrogen-bonding networks with hydroxyl groups on the functionalized nanotubes. According to the paper, this interfacial architecture helped produce highly aligned and densely packed nanotube networks while strengthening interfacial interactions inside the fibers.

The best performance was obtained at a PBO content of 20 wt.%. At this composition, the composite fibers reached a tensile strength of 3.52 GPa, a Young’s modulus of 306 GPa, and a toughness of 71.5 MJ/m³. The toughness was 2.7 times that of pristine fibers. The optimized fibers also showed electrical conductivity of 3.65 MS/m and a specific penetration energy of about 1.39 MJ/kg under high-speed impact, exceeding that of Kevlar fibers reported in the paper’s comparison. Multiscale structural analysis showed that this composition gave the highest nanotube orientation, the lowest void volume, and stronger interfacial interactions.

“In this work, we show that reinforcing intertube interactions through a hydrogen-bonding interface can improve alignment, densification, and stress transfer at the same time,” said Muqiang Jian, corresponding author of the study. “That combination is important for moving carbon nanotube fibers closer to real structural and protective applications.” The team also used in situ Raman spectroscopy, stress-relaxation analysis, and fracture morphology observations to probe the mechanism, supporting the role of hydrogen-bonding-mediated interfaces in suppressing nanotube slippage and improving load transfer efficiency.

The authors note that current carbon nanotube fibers still remain below commercial high-performance fibers such as carbon fibers and PBO fibers in overall mechanical performance. Their next steps include increasing nanotube aspect ratio and dope concentration, optimizing flow-field design and spinning parameters, and further engineering intertube interactions to improve load transfer efficiency.

“This study provides a scalable design strategy for structure-function-integrated carbon nanotube fibers,” said Yongyi Zhang, corresponding author of the study. “We expect it to be useful for the development of lightweight fibers for structural and impact-resistant applications.” 

This work was supported by the National Key Research and Development Program of China, the National Natural Science Foundation of China, the Beijing National Laboratory for Molecular Sciences, the Beijing Natural Science Foundation, the Strategic Priority Research Program of the Chinese Academy of Sciences, and the Shenzhen Science and Technology Innovation Commission. 

DOI Link:

https://doi.org/10.26599/NR.2026.94908598

About Nano Research

Nano Research is a peer-reviewed, open access, international and interdisciplinary research journal, sponsored by Tsinghua University and the Chinese Chemical Society, published by Tsinghua University Press on the platform SciOpen. It publishes original high-quality research and significant review articles on all aspects of nanoscience and nanotechnology, ranging from basic aspects of the science of nanoscale materials to practical applications of such materials. After 18 years of development, it has become one of the most influential academic journals in the nano field. Nano Research has published more than 1,000 papers every year from 2022, with its cumulative count surpassing 8,000 articles. In 2025 InCites Journal Citation Reports, its 2025 IF is 9.4 (8.3, 5 years), and it continues to be the Q1 area among the four subject classifications. Nano Research Award, established by Nano Research together with TUP and Springer Nature in 2013, and Nano Research Young Innovators (NR45) Awards, established by Nano Research in 2018, have become international academic awards with global influence.