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

Abstract

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.

Fig. 1: Kevlar-inspired AAs self-assemble into ultra-stable nanoribbons capable of hierarchical ordering to form dry macroscopic threads.
Fig. 2: AA nanoribbons exhibit minimal molecular exchange.
Fig. 3: AA nanoribbons have a Young’s modulus of E = 1.7 GPa and a tensile strength of σ* = 1.9 GPa.
Fig. 4: AA nanoribbons are aligned by shear forces and dried to form flexible threads.
Fig. 5: X-ray scattering of solid-state nanoribbon threads demonstrates organized molecular packing, extended hydrogen bonding networks and long-range hierarchical order.

Data availability

The data generated and analysed during this study are available from the corresponding author on reasonable request.

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Acknowledgements

We thank E. Deiss-Yehiely and C. Settens for their helpful input. We thank R. Allen and L. Hopkins for contributing graphics shown in the figures. We acknowledge J. Tian and S. Kallakuri for contributions to synthesis of early stage AAs that led to the molecular designs incorporated in this report. This material is based upon work supported by the National Science Foundation under grant no. CHE-1945500. This work was supported in part by the Professor Amar G. Bose Research Grant Program, the Abdul Latif Jameel Water and Food Systems Lab, and the MIT Center for Environmental Health Sciences under NIH Center grant P30-ES002109. D.-Y.K. acknowledges the support of the National Research Foundation of Korea’s Basic Science Research Program and Chonbuk National University Fellowship Program. T.C.-T. and W.R.L. acknowledge the support of the National Science Foundation Graduate Research Fellowship Program under grant no. 1122374. T.C.-T. acknowledges the support of the Martin Family Society of Fellows for Sustainability. G.L. acknowledges support from the Université d’Evry-Paris Saclay. This work made use of the MRSEC Shared Experimental Facilities at MIT supported by the National Science Foundation under award number DMR-14-19807 and the MIT Department of Chemistry Instrumentation Facility. X-ray scattering measurements were performed at beamline 12-ID-B of the Advanced Photon Source, a US Department of Energy Office of Science User Facility operated for the US Department of Energy Office of Science by Argonne National Laboratory under contract no. DE-AC02-06CH11357. This work was performed in part at the Harvard University Center for Nanoscale Systems cryo-TEM facility, a member of the National Nanotechnology Coordinated Infrastructure Network, which is supported by the National Science Foundation under award no. 1541959.

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T.C.-T., D.-Y. K. and J.H.O. conceived and designed the experiments. D.-Y.K. and T.C.-T. synthesized materials with assistance from W.R.L. and A.J.L.; T.C.-T. and D.-Y.K. performed chemical characterization of all samples. T.C.-T. performed conventional TEM and cryo-TEM. Y.C. and T.C.-T. performed SEM. G.L. performed AFM and statistical topographical analyses. G.L. performed sonication-induced scission measurements, imaging with AFM and TEM, and analysis of data. A.J.L. performed FRET measurements and analysis of the data. X.Z., T.C.-T. and Y.C. performed solution X-ray scattering and analysis of the data. A.J.L. and Y.C. conceptualized nanoribbon thread processing, and Y.C. and M.G. prepared nanoribbon threads. M.G. performed tensile testing of nanoribbon threads and analysis of the data. T.C.-T. and Y.C. performed X-ray scattering of solid-state nanoribbon threads and analysis of the data. J.H.O., T.C.-T and Y.C. cowrote the manuscript. J.H.O. provided project administration, funding acquisition and supervision. All authors discussed the results and commented on the manuscript.

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Correspondence to Julia H. Ortony.

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Christoff-Tempesta, T., Cho, Y., Kim, DY. et al. Self-assembly of aramid amphiphiles into ultra-stable nanoribbons and aligned nanoribbon threads. Nat. Nanotechnol. (2021). https://doi.org/10.1038/s41565-020-00840-w

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