Researchers construct molecular nanofibers that are stronger than steel

MIT News  January 25, 2021
Small-molecule self-assembly is an established route for producing high-surface-area nanostructures with readily customizable chemistries and precise molecular organization. The whole structure falls apart when you remove water, particularly when any kind of external force is applied. An international team of researchers (USA – MIT, Argonne National Laboratory, France) has shown that a small-molecule platform, the aramid amphiphile 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. They exploited this stability to extend small-molecule self-assembly to hierarchically ordered macroscopic materials outside of solvated environments. Through an aqueous shear alignment process, they organized 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. The research has promise for miniaturizing technologies by performing more chemistry with less material…read more. TECHNICAL ARTICLE 

…Parts of the molecules attracted to or repulsed from water, shown in purple and blue respectively, orient and guide the molecules to form a nanostructure… Credit: Peter Allen

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