Self-assembly of aramid amphiphiles into ultra-stable nanoribbons and aligned nanoribbon threads

• Published in: Nature nanotechnology Vol. 16; no. 4; pp. 447 - 454
• Main Authors: Christoff-Tempesta, Ty, Cho, Yukio, Kim, Dae-Yoon, Geri, Michela, Lamour, Guillaume, Lew, Andrew J., Zuo, Xiaobing, Lindemann, William R., Ortony, Julia H.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 01.04.2021; Nature Publishing Group
• Subjects: 639/301/357; 639/638/541; Aramid fibers; Chemical Physics; Chemistry; Chemistry and Materials Science; Composite materials; Design; Drying; Exchanging; Hydrogen bonds; Kevlar (trademark); Materials Science; Mechanical properties; Modulus of elasticity; Molecular structure; Nanomaterials; Nanoribbons; Nanoscale materials; NANOSCIENCE AND NANOTECHNOLOGY; Nanotechnology; Nanotechnology and Microengineering; Physics; Self-assembly; Solid state; Supramolecular chemistry; Tensile strength; Tensile tests
• DOI: 10.1038/s41565-020-00840-w
• ISSN: 1748-3387; 1748-3395

Small-molecule self-assembly is an established route for producing high-surface-area nanostructures with readily customizable chemistries and precise molecular organization. However, these structures are fragile, exhibiting molecular exchange, migration and rearrangement—among other dynamic instabilities—and are prone to dissociation upon drying. Here we show a small-molecule platform, the aramid amphiphile, that overcomes these dynamic instabilities by incorporating a Kevlar-inspired domain into the molecular structure. Strong, anisotropic interactions between aramid amphiphiles suppress molecular exchange and elicit spontaneous self-assembly in water to form nanoribbons with lengths of up to 20 micrometres. Individual nanoribbons have a Young’s modulus of 1.7 GPa and tensile strength of 1.9 GPa. We exploit this stability to extend small-molecule self-assembly to hierarchically ordered macroscopic materials outside of solvated environments. Through an aqueous shear alignment process, we organize aramid amphiphile nanoribbons into arbitrarily long, flexible threads that support 200 times their weight when dried. Tensile tests of the dry threads provide a benchmark for Young’s moduli (between ~400 and 600 MPa) and extensibilities (between ~0.6 and 1.1%) that depend on the counterion chemistry. This bottom-up approach to macroscopic materials could benefit solid-state applications historically inaccessible by self-assembled nanomaterials. Self-assembled nanoribbons with extensive and collective intermolecular interactions exhibit robust mechanical properties, enabling their translation to macroscopic solid-state threads.