Solvent Effects on the Mechanical Enhancement of Wet-Drawn Carbon Nanotube Assemblies

Macroscopic carbon nanotube assemblies (CNTAs) have advanced mechanical, electrical, and optical properties and exhibit potential applications in a wide range of technological fields. These properties stem from the intrinsic structural features of individual carbon nanotubes (CNTs). Wet-drawing is the most prevalent technique in optimizing the structure of CNTAs in both academia and industry. However, the understanding of the fundamental mechanisms governing the efficacy of the wet-drawing process remains insufficient. In this work, we investigated the influence of solvents on the structural evolution of CNTAs during wet-drawing and their impact on mechanical properties via coarse-grained molecular dynamics (CGMD) simulations. Our study revealed a volcano-like relationship between an energy parameter (ε) and the assembly strength, indicating that ε significantly influences the wetting behavior of solvents toward CNTAs. An increased ε value leads to decreased orientation entropy during drawing and increased entropy during solvent evaporation, elucidating the mechanisms underlying solvent-CNT interactions. To further validate our findings, we conducted experiments using five solvents with different energy parameters. The observed trends in mechanical, electrical, and optical properties were consistent with theoretical predictions. This work establishes a framework for solvent selection to enhance CNTAs' performance, advancing their applications in high-end areas.