Ultra-High Toughness Fibers Using Controlled Disorder of Assembled Aramid Nanofibers

Abstract

Assembling nanoscale building blocks with reduced defects has emerged as a promising approach to exploit nanomaterials in the fabrication of simultaneously strong and tough architectures at larger scales. Aramid nanofibers (ANFs), a type of organic nanobuilding block, have been spotlighted due to their superior mechanical properties and thermal stability. However, no breakthrough research has been conducted on the high mechanical properties of a structure composed of ANFs. Here, assembling ANFs into macroscale fiber using a simultaneous protonation and wet-spinning process is studied to reduce defects and control disorder. The ANF-assembled fibers consist of hierarchically aligned nanofibers that behave as a defective law structure, making it possible to reach a Young’s modulus of 53.15 ± 8.98 GPa, a tensile strength of 1,353.64 ± 92.98 MPa, and toughness of 128.66 ± 14.13 MJ m−3. Compared to commercial aramid fibers, the fibers exhibit ≈1.6 times greater toughness while also providing specific energy to break as 93 J g−1. Furthermore, this shows recyclability of the ANF assembly by retaining ≈94% of the initial mechanical properties. This study demonstrates a facile process to produce high stiffness and strength fibers composed of ANFs that possess significantly greater toughness than commercial synthetic fibers.A novel aramid nanofibers assembly strategy for macroscale fibers using a simultaneous protonation and wet-spinning process along with drawing and annealing processes is reported. The prepared fibers show hierarchically aligned nanofibers as a defective law structure, making it possible to reach greater specific toughness compared to existing commercial synthetic and natural fibers, which corresponds to spider silks while showing higher strength and modulus than spider silks.