@article{5d97425e76f14624bcbf1601dd2e8ac1,
title = "Cooperative Self-Assembly of Pyridine-2,6-Diimine-Linked Macrocycles into Mechanically Robust Nanotubes",
abstract = "Nanotubes assembled from macrocyclic precursors offer a unique combination of low dimensionality, structural rigidity, and distinct interior and exterior microenvironments. Usually the weak stacking energies of macrocycles limit the length and mechanical strength of the resultant nanotubes. Imine-linked macrocycles were recently found to assemble into high-aspect ratio (>103), lyotropic nanotubes in the presence of excess acid. Yet these harsh conditions are incompatible with many functional groups and processing methods, and lower acid loadings instead catalyze macrocycle degradation. Here we report pyridine-2,6-diimine-linked macrocycles that assemble into high-aspect ratio nanotubes in the presence of less than 1 equiv of CF3CO2H per macrocycle. Analysis by gel permeation chromatography and fluorescence spectroscopy revealed a cooperative self-assembly mechanism. The low acid concentrations needed to induce assembly enabled nanofibers to be obtained by touch-spinning, which exhibit higher Young's moduli (1.33 GPa) than many synthetic polymers and biological filaments. These findings represent a breakthrough in the design of inverse chromonic liquid crystals, as assembly under such mild conditions will enable the design of structurally diverse and mechanically robust nanotubes from synthetically accessible macrocycles.",
keywords = "organic nanotubes, self-assembly, stimuli responsive materials, supramolecular chemistry, touch-spinning",
author = "Strauss, {Michael J.} and Darya Asheghali and Evans, {Austin M.} and Li, {Rebecca L.} and Chavez, {Anton D.} and Chao Sun and Becker, {Matthew L.} and Dichtel, {William R.}",
note = "Funding Information: This work was funded by the Army Research Office through the Multidisciplinary University Research Initiative (MURI; W911NF-15-1-0447, to W.R.D.). M.J.S. was supported by the National Science Foundation (NSF) through the Graduate Research Fellowship Program (GRFP) under Grant No. (DGE-1842165.). A.M.E. was supported by the National Science Foundation (NSF) through the Graduate Research Fellowship Program (GRFP) under Grant No. (DGE-1324585). This work made use of the Integrated Molecular Structure Education and Research Center (IMSERC) at Northwestern University, which has received support from the National Science Foundation (NSF; CHE-1048773), the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF; NNCI-1542205), the State of Illinois, and the International Institute for Nanotechnology (IIN). This work also made use of the Scanned Probe Imaging and Development (SPID), and the Electron Probe Instrumentation Center (EPIC), facilities of Northwestern University's Atomic and Nanoscale Characterization Experiment Center (NUANCE), which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF; ECCS-1542205); the MRSEC program (NSF; DMR-1720139) at the Materials Research Center; the International Institute for Nanotechnology (IIN); the Keck Foundation; and the State of Illinois. This work was also supported by the Northwestern University Keck Biophysics Facility and a Cancer Center Support Grant (NCI CA060553). Parts of this work were performed at the DuPoint-Northwestern-Dow Collaborative Access Team (DND-CAT) located at Sector 5 of the Advanced Photon Source (APS) at Argonne National Lab. This research used resources of the Advanced Photon Source and the Center for Nanoscale Materials, both U.S. Department of Energy (DOE) Office of Science User Facilities operated for the DOE Office of Science by Argonne National Laboratory under Grant No. (DGE-1324585). M.L.B. acknowledges support from the Ohio Third Frontier (Akron Functional Materials Center). We acknowledge Prof. Todd Blackledge and Angela Alicea for their assistance with the UTM NanoBionix tensile tester. We acknowledge Thomas Fitzsimons (Whiff L.L.C.) for preparing the touch-spinning prototype. We acknowledge Joseph Accardo for helpful discussions and Prof. Julia Kalow for the use of her GPC instrument. Publisher Copyright: {\textcopyright} 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim",
year = "2019",
month = oct,
day = "7",
doi = "10.1002/anie.201907668",
language = "English (US)",
volume = "58",
pages = "14708--14714",
journal = "Angewandte Chemie - International Edition",
issn = "1433-7851",
publisher = "John Wiley and Sons Ltd",
number = "41",
}