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Description:

Most mechanochromic luminescent compounds are crystalline and highly hydrophobic; however, mechanochromic luminescent molecular assemblies comprising amphiphilic molecules have rarely been explored. This study investigated mechanochromic luminescent supramolecular fibers composed of dumbbell-shaped 9,10-bis(phenylethynyl)anthracene-based amphiphiles without any tetraethylene glycol (TEG) substituents or with two TEG substituents. Both amphiphiles formed water-insoluble supramolecular fibers via linear hydrogen bond formation. Both compounds acquired water solubility when solid samples composed of supramolecular fibers were ground. Grinding induces the conversion of one-dimensional supramolecular fibers into micellar assemblies where fluorophores can form excimers, thereby resulting in a large redshift in the fluorescence spectra. Excimer emission from the ground amphiphile without TEG chains was retained after dissolution in water. The micelles were stable in water because hydrophilic dendrons surrounded the hydrophobic luminophores. By contrast, when water was added to a ground amphiphile having TEG substituents, fragmented supramolecular fibers with the same molecular arrangement as the initial supramolecular fibers were observed, because fragmented fibers are thermodynamically preferable to micelles as the hydrophobic arrays of fluorophores are covered with hydrophilic TEG chains. This leads to the recovery of the initial fluorescent properties for the latter amphiphile. These supramolecular fibers can be used as practical mechanosensors to detect forces at the mesoscale.

Rights:

• Creative Commons BY Attribution 4.0 International
  

Keyword: supramolecular polymers, mechanochromic luminescence, grind-induced water solubility, atomic force microscopy, transmission electron microscopy

Date published: 2024-03-10

Publisher: Wiley

Journal:

• Small (ISSN: 16136810) p. 1613-1613 2400063

Funding:

• Core Research for Evolutional Science and Technology JPMJCR20B2
• Japan Society for the Promotion of Science JP23H04878
• Japan Society for the Promotion of Science JP23H04874
• Japan Society for the Promotion of Science JP23H04879
• Japan Society for the Promotion of Science JP16K17885

Manuscript type: Publisher's version (Version of record)

MDR DOI:

First published URL: https://doi.org/10.1002/smll.202400063

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Updated at: 2024-08-19 16:30:14 +0900

Published on MDR: 2024-08-19 16:30:14 +0900