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Qiming Liu, Tianyue Zhang, Yuka Ikemoto, Yudai Shinozaki, Go Watanabe, Yuta Hori, Yasuteru Shigeta, Takemi Midorikawa, [Koji Harano](https://orcid.org/0000-0001-6800-8023), Yoshimitsu Sagara

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[Grinding‐Induced Water Solubility Exhibited by Mechanochromic Luminescent Supramolecular Fibers](https://mdr.nims.go.jp/datasets/029716bf-b963-4607-8135-26876c20f656)

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Grinding‐Induced Water Solubility Exhibited by Mechanochromic Luminescent Supramolecular FibersRESEARCH ARTICLEwww.small-journal.comGrinding-Induced Water Solubility Exhibited byMechanochromic Luminescent Supramolecular FibersQiming Liu, Tianyue Zhang, Yuka Ikemoto, Yudai Shinozaki, Go Watanabe, Yuta Hori,Yasuteru Shigeta, Takemi Midorikawa, Koji Harano, and Yoshimitsu Sagara*Most mechanochromic luminescent compounds are crystalline and highlyhydrophobic; however, mechanochromic luminescent molecular assembliescomprising amphiphilic molecules have rarely been explored. This studyinvestigated mechanochromic luminescent supramolecular fibers composedof dumbbell-shaped 9,10-bis(phenylethynyl)anthracene-based amphiphileswithout any tetraethylene glycol (TEG) substituents or with two TEGsubstituents. Both amphiphiles formed water-insoluble supramolecular fibersvia linear hydrogen bond formation. Both compounds acquired watersolubility when solid samples composed of supramolecular fibers are ground.Grinding induces the conversion of 1D supramolecular fibers into micellarassemblies where fluorophores can form excimers, thereby resulting in a largeredshift in the fluorescence spectra. Excimer emission from the groundamphiphile without TEG chains is retained after dissolution in water. Themicelles are stable in water because hydrophilic dendrons surround thehydrophobic luminophores. By contrast, when water is added to a groundamphiphile having TEG substituents, fragmented supramolecular fibers withthe same molecular arrangement as the initial supramolecular fibers areobserved, because fragmented fibers are thermodynamically preferable tomicelles as the hydrophobic arrays of fluorophores are covered withhydrophilic TEG chains. This leads to the recovery of the initial fluorescentproperties for the latter amphiphile. These supramolecular fibers can be usedas practical mechanosensors to detect forces at the mesoscale.Q. Liu, T. Zhang, Y. SagaraDepartment of Materials Science and EngineeringTokyo Institute of Technology2-12-1 Ookayama, Meguro-ku, Tokyo 152–8552, JapanE-mail: sagara.y.aa@m.titech.ac.jpY. IkemotoJapan Synchrotron Radiation Research Institute/SPring-81-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679–5198, JapanY. Shinozaki, G. WatanabeDepartment of PhysicsSchool of ScienceKitasato University1-15-1 Kitazato, Minami-ku, Sagamihara, Kanagawa 252–0373, JapanThe ORCID identification number(s) for the author(s) of this articlecan be found under https://doi.org/10.1002/smll.202400063© 2024 The Authors. Small published by Wiley-VCH GmbH. This is anopen access article under the terms of the Creative Commons AttributionLicense, which permits use, distribution and reproduction in anymedium, provided the original work is properly cited.DOI: 10.1002/smll.2024000631. IntroductionOver the past 20 years, a vast numberof organic compounds and organometal-lic complexes capable of changing theirluminescence properties in response tomechanical stimuli have been developedowing to their potential applications insensors and memory.[1–7] In most cases, theobserved changes in luminescence proper-ties were not caused by the force-inducedcleavage of covalent bonds within the com-pound. Rather, they result from alterationsin the molecular assembly, which is formedby the combination of various intermolec-ular interactions, such as hydrogen bonds,𝜋-stacking, hydrophobic effect, and dipole–dipole interaction. Mechanochromic lumi-nescent materials are ideal for detectingforces applied to hydrophobic materials,such as glass, metals, and polymers, aswell as for detecting and visualizing theforces applied to or generated by living cellsand other biomaterials. However, most re-ported organic[8–37] or organometallic[38–46]compounds cannot be utilized for thelatter purpose because of their high crys-tallinity and/or hydrophobic molecularG. WatanabeDepartment of Data ScienceSchool of Frontier EngineeringKitasato University1-15-1 Kitazato, Minami-ku, Sagamihara, Kanagawa 252–0373, JapanG. WatanabeKanagawa Institute of Industrial Science and Technology (KISTEC)705–1 Shimoimaizumi, Ebina, Kanagawa 243–0435, JapanY. Hori, Y. ShigetaCenter for Computational SciencesUniversity of Tsukuba1-1-1 Tennodai, Tsukuba, Ibaraki 305–8577, JapanT. Midorikawa, K. HaranoCenter for Basic Research on MaterialsNational Institute for Materials Science1-1 Namiki, Tsukuba, Ibaraki 305-0044, JapanK. Harano, Y. SagaraLiving Systems Materialogy (LiSM) Research GroupInternational Research Frontiers Initiative (IRFI)Tokyo Institute of Technology4259 Nagatsuda-cho, Midori-ku, Yokohama, Kanagawa 226–8503, JapanSmall 2024, 20, 2400063 © 2024 The Authors. Small published by Wiley-VCH GmbH2400063 (1 of 10)http://www.small-journal.commailto:sagara.y.aa@m.titech.ac.jphttps://doi.org/10.1002/smll.202400063http://creativecommons.org/licenses/by/4.0/http://crossmark.crossref.org/dialog/?doi=10.1002%2Fsmll.202400063&domain=pdf&date_stamp=2024-03-10www.advancedsciencenews.com www.small-journal.comstructures. Moreover, compounds with hydrophilic molecularstructures are highly limited[47–53] compared with hydrophobicmechanochromic luminescent compounds, which have beenwidely developed. Though a number of amphiphiles are knownto form a variety types of molecular assembled structuresincluding micelles, cylindrical micelles, vesicles, and planermembranes,[54–59] their mechanoresponsiveness has not beenwell investigated.One challenge in utilizing mechanochromic fluorescent ma-terials as practical mechanosensors is achieving quantification.Many existing crystalline materials have yet to address this is-sue. Crystalline materials, comprising numerous micro- andnanocrystals, exhibit a wide range of particle sizes. Consequently,the forces required to induce changes in molecular assembly dif-fer; larger crystals need significant force to break, while smallercrystals can be broken with considerably less force. Addition-ally, due to their composition of a large number of molecules,crystalline compounds require a relatively large force to inducechanges in luminescence properties. This characteristic of crys-talline compounds spoils the advantage of mechanochromic ma-terials based on alterations in molecular arrangement, whichcan elicit changes in luminescence properties with inherentlyweaker forces, as there is no need to break covalent bonds.Addressing these inherent issues in practical applications re-quires the construction of molecular assemblies that exhibitmechanochromic fluorescent properties with a uniform and lim-ited number of molecules. Rather than constructing 3D molecu-lar assemblies comprising a vast number of molecules, a low-dimensional molecular assembly should be pursued to detectvery small forces and maintain uniform thresholds. Potentialmolecular assemblies include micelle-like aggregates with uni-form size, 1D supramolecular fibers, and 2D molecular sheets ofuniform thickness.In 2014, a study reported that mechanochromic fluorescentmicelles change their fluorescent color upon mechanical stimula-tion in water; these micelles were composed of 10–15 dumbbell-shaped amphiphiles.[50] In brief, 1,6-bis(phenylethynyl)pyrenewas introduced as a luminescent group at the center of theamphiphile. Hydrophilic dendrons with multiple hydroxyl andamino groups at the periphery were attached to the luminophorevia amide groups. In water, the amphiphile self-assembled intomicelles, in which hydrogen bonds formed between the amidegroups, and the fluorescent cores 𝜋-stacked to form a static ex-cimer. Note that when micelles are loaded onto glass or polymerbeads using commercially available crosslinkers, and sufficientforce is applied, the arrangement of the luminophores changes,thus preventing them from forming excimers. This conversionresults in a blueshift in the fluorescence spectrum. Because themicelles have almost the same size, a threshold of force exists toinduce a change in the fluorescence color from yellow to green,which is suitable for practical mechanosensors. However, to in-duce the fluorescence color change in the micelles, all 𝜋-stackedarrangements of fluorophores must be changed into an arrange-ment that does not contain any excimers. If an excimer site exists,energy transfer occurs from other monomer-like regions, thusresulting in excimer-dominant fluorescence. Consequently, thesensitivity of the micelles is poor to mechanical stimuli.To address these issues, this study investigated twomechanochromic supramolecular fibers consisting of am-phiphiles with different hydrophilicities (Figure 1). Further, me-chanical grinding endows the amphiphiles with water solubilityowing to the transformation of their molecular assemblies. Tothe best of our knowledge, this is the first report of force-inducedwater solubility, accompanied by mechanochromic lumines-cence. The supramolecular fibers consisted of dumbbell-shapedamphiphiles based on 9,10-bis(phenylethynyl)anthracene, with-out or with tetraethylene glycol (TEG) chains on the fluorophore(Figure 1a). The present supramolecular fibers exhibited agrinding-induced redshift of the emission spectra, which isopposite to the blueshift observed in the emission of previouslyreported micelles.[50] The initial supramolecular fibers did notexhibit excimer fluorescence. By grinding in the solid states, themolecular assembly structures of the 1D fiber were convertedto micellar structures, and the emitters formed excimers, thuscausing the red shift of emission. Note that if even one excimerforms at any location within the 1D fibers, energy transfer occursfrom the monomer-like fluorophores in the vicinity, thus leadingto excimer-dominant fluorescence. Consequently, the sensitivityof the fiber far exceeded those of previous mechanochromicluminescent micelles. After the addition of water to the groundsamples of amphiphiles without and with TEG chains, bothsamples became water-soluble, and different responses wereobserved (Figure 1b). In the former, without TEG groups,the excimer fluorescence was maintained in water becausethe micellar structures were stable and retained in water. Bycontrast, the latter, with TEG groups, recovered their initialfluorescent properties through conversion from thermody-namically unfavorable micellar structures to stable fragmentedfibers. Given that such mechanochromic supramolecular fiberspossess a width equivalent to that of a single molecule, theycould serve as practical mechanosensing fluorescent materialsif uniformly dispersed onto other materials. The fluorescencecolor would change upon the application of a force exceedinga certain threshold, with the magnitude of this force beingvery small.Recently, supramolecular mechanophores capable of detectingpN-order forces at the single-molecule level were developed.[60–68]However, to use these mechanophores as molecular tools for de-tecting forces at the mesoscale level, they need to be introducedinto polymers or supported on the surfaces of other materials.By contrast, the supramolecular fibers developed in this studyare continuous molecular aggregates with lengths in the order ofmicrometers and can be used as is in mesoscale, which is highlyadvantageous.2. Results and DiscussionThe molecular structures of the 9,10-bis(phenylethynyl)anthracene derivatives 1 and 2 are shownin Figure 1. Two hydrophilic dendritic structures with twelvehydroxy groups at the peripheral positions were introducedinto the fluorophore through amide groups to form hydrogenbonds in the molecular assemblies. Given that the fluorophoreis hydrophobic, dumbbell-shaped compounds 1 and 2 areamphiphiles. In addition, two TEG chains were introduced tothe fluorophore of 2 to enhance its hydrophilicity. Reportedly,several dumbbell-shaped amphiphiles exhibit mechanochromicluminescence.[48,50,51] A dumbbell-shaped pyrene derivative withSmall 2024, 20, 2400063 © 2024 The Authors. Small published by Wiley-VCH GmbH2400063 (2 of 10) 16136829, 2024, 33, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/smll.202400063 by Cochrane Japan, Wiley Online Library on [15/08/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.small-journal.comwww.advancedsciencenews.com www.small-journal.comFigure 1. a) Molecular structures of amphiphiles 1 and 2, along with schematics of each amphiphile. b) Schematic of the external stimuli-induced changein the molecular assembly of mechanochromic luminescence supramolecular fibers consisting of amphiphiles 1 (top) or 2 (bottom).two bulky water-soluble dendritic structures was reported toexhibit reversible fluorescent color changes upon mechanicalstimulation and exposure to water vapor in the solid phase.[48]Additionally, a pyrene derivative with reduced dendron bulkinessreportedly forms mechanochromic luminescent micelles.[50] Forthese dumbbell-shaped amphiphiles, dendrons were introducedalong the long axis of the fluorophore. By contrast, for com-pounds 1 and 2, the substitution positions of the dendronsare tilted 60° from the long axis of the luminophore, therebyresulting in a sheared, dumbbell-like molecular structure.These amphiphiles were expected to enable access to thermo-dynamically stable molecular assemblies other than micelles.Amphiphiles 1 and 2 were synthesized via Sonogashira couplingbetween 9,10-diiodoanthracene and dendritic groups in whichall twelve hydroxyl groups were protected with triisopropylsilyl(TIPS) groups; subsequently, the TIPS groups were depro-tected. Both 1 and 2 were characterized by 1H and 13C NMRspectroscopy and high-resolution electrospray ionization massspectroscopy (see Supporting Information).First, the absorption and fluorescence properties of 1 and2 in solution were examined. Compound 1 in the mixture ofchloroform and methanol (1:1, v/v) exhibited peaks at 464 nm(𝜖 = 3.9× 104 L mol−1 cm−1), 440 nm (𝜖 = 3.7× 104 L mol−1 cm−1),and 273 nm (𝜖 = 1.3 × 105 L mol−1 cm−1) in the absorp-tion spectrum (Figure 2a, left). In the emission spectrum,the solution exhibited two peaks, at 478 and 509 nm, andone shoulder at ≈540 nm, indicating a vibronic structure(Figure 2a, right). These spectral features are typical of 9,10-bis(phenylethynyl)anthracene luminophores in the monomericstate in solution.[35–37,69,70] The TEG chains allowed 2 to be solu-ble in more polar solvents and slightly changed its photophysi-cal properties because of their electron-donating nature. The ab-sorption spectrum of 2 in methanol exhibited peaks at 478 nm(𝜖 = 5.4× 104 L mol−1 cm−1), 450 nm (𝜖 = 4.4× 104 L mol−1 cm−1),and 275 nm (𝜖 = 1.2 × 105 L mol−1 cm−1) (Figure 2b, left). Thehighest emission peak was observed at 492 nm, which was red-shifted compared with that of 1 in solution (Figure 2b, right). Am-phiphiles 1 and 2 showed good quantum yields: 0.94 in a mixtureof chloroform and methanol (1:1, v/v) and 0.84 in methanol, re-spectively. Additionally, a monomer emission lifetime of 3.0 nswas calculated from the emission decay profiles recorded for thediluted solutions of 1 and 2 (Figure S1, Supporting Information).Small 2024, 20, 2400063 © 2024 The Authors. Small published by Wiley-VCH GmbH2400063 (3 of 10) 16136829, 2024, 33, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/smll.202400063 by Cochrane Japan, Wiley Online Library on [15/08/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.small-journal.comwww.advancedsciencenews.com www.small-journal.comFigure 2. Absorption (left) and photoluminescence (right) spectra of a) amphiphile 1 in chloroform/methanol (1:1 v/v, blue line; 11.5:1 v/v, red line)and b) amphiphile 2 in methanol (blue line) and in water/methanol (7:3 v/v, red line). c = 1.0 × 10−5 m. The photoluminescence spectra were recordedwith an excitation light of 400 nm.Changing the solvent polarity altered the absorption spectraof 1 and 2 in solution. Increasing the ratio of chloroform re-sulted in the precipitation of compound 1 and redshift of the ab-sorption band between 400 and 500 nm with peaks at 489 and458 nm (Figure 2a, left). As partial precipitation occurred, the ab-sorbance decreased. A more pronounced redshift was observedfor 2 when water was added to the methanol solution. The ab-sorption peak at the longest wavelength redshifted from 478 to510 nm (Figure 2b, left). The baseline of the absorption spectrumwas elevated because of light scattering from the aggregates. Theredshifts in the absorption spectra of these amphiphiles suggestthat the fluorophores formed J-aggregate-like arrangements.[71,72]The larger shift observed for 2 indicates that the fluorophore ar-rangements were different in 1 and 2. The fluorescence spec-trum of 2 also showed a large redshift when molecular aggregateswere formed upon the addition of water, displaying peaks at 525and 552 nm (Figure 2b, right). No significant redshift occurredin the fluorescence spectrum of 1, presumably because numer-ous molecules in the monomeric state remained in the solution(Figure 2a, right). Notably, no excimer emission was observed forboth solutions of 1 or 2 containing supramolecular assemblies.Atomic force microscopy (AFM) and transmission electron mi-croscopy (TEM) were used to elucidate the nature of the molec-ular assemblies of 1 and 2 in solution. The AFM images of thesamples prepared by coating a chloroform/methanol (9:1, v/v) so-lution of 1 on mica (Figure 3a left; Figure S2, Supporting Infor-mation) show numerous fibers with a height of ≈1.5 nm. Someof the observed supramolecular fibers were over 1 μm in length.Supramolecular fibers were also observed in the TEM imagesof the sample prepared by coating the same solution onto anamorphous carbon film without staining (Figure 3a right; FigureS3, Supporting Information). The width of the supramolecularfiber was ≈5–6 nm, which corresponds to the length of 1. Thelow height of the fibers observed in AFM images suggests that1 was not stacked in a completely overlapping manner perpen-dicular to the direction of the fiber but rather in a tilted man-ner (Figure S4a, Supporting Information). 1D supramolecularfibers were also observed in the AFM images of the samples pre-pared from a water/methanol (7:3, v/v) solution of 2 (Figure 3bleft; Figure S5, Supporting Information). Some fibers were at-tached to form a single strand, whereas others were branched.Longer and more flexible fibers were observed compared withthe supramolecular fibers consisting of 1. The height of the fiberswas more distributed in the case of compound 2. The TEM im-ages also clarified that the fibers had the width of individualmolecules (≈5 nm; Figure 3b right and Figure S6, SupportingInformation). These results suggest that amphiphile 2 formedmore hydrophilic supramolecular fibers (Figure S4b, SupportingInformation) in a mixture of water and methanol owing to theTEG chains.Infrared (IR) spectroscopic measurements were conducted toconfirm that both amphiphiles formed intermolecular hydrogenbonds between the amide groups (Figure 4, top). Because thelarge absorption bands attributed to OH stretching mask peaksSmall 2024, 20, 2400063 © 2024 The Authors. Small published by Wiley-VCH GmbH2400063 (4 of 10) 16136829, 2024, 33, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/smll.202400063 by Cochrane Japan, Wiley Online Library on [15/08/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.small-journal.comwww.advancedsciencenews.com www.small-journal.comFigure 3. AFM (left) and TEM (right) images of supramolecular fibers consisting of a) 1 and b) 2. The insets in the left panels show the height profilesof the supramolecular fibers. The insets in the right panels show magnified views of the areas enclosed by the dotted lines. The TEM images were takenwithout staining. Solutions of 1 in chloroform/methanol (9:1 v/v) and solutions of 2 in water/methanol (7:3 v/v) were used for sample preparation.ascribed to N-H stretching of the amide groups, the C=O stretch-ing of the amide groups was investigated for solid samples con-sisting of supramolecular fibers of 1 and 2. The former samplewas prepared by slow evaporation of a dichloroethane/methanolFigure 4. Partial IR spectra of a) 1 and b) 2 in the initial solid (top), groundstates (middle), and dried films after the addition of water to ground sam-ples (bottom).solution of 1. Whereas the latter was obtained by removing mostof the methanol from a methanol/water solution of compound2 using an evaporator, followed by lyophilization. Amphiphiles 1and 2 exhibited a peak at 1648 and 1640 cm−1, respectively, in-dicating that the amide groups of both compounds formed in-termolecular hydrogen bonds in the fibers, and no peaks corre-sponding to free amide groups were observed. The sharp peakssuggested the formation of uniform linear hydrogen bonds. Be-cause the peak positions were different, the hydrogen bondingmodes in the supramolecular fibers were also different, suggest-ing that the fluorophore arrangements are different from eachother. These results are in good agreement with the fact that com-pound 2 exhibits a pronounced redshift of the absorption band,as shown in Figure 2.The highest occupied molecular orbital (HOMO) and low-est unoccupied molecular orbital (LUMO) pictures and transi-tion dipole moments for model compounds identical to the cen-tral molecular structures of 1 and 2 were calculated (Figures S7and S8, Supporting Information). The HOMO and LUMO ofboth models lay primarily in the anthracene group. Both tran-sition dipole moments were slightly tilted from the long axis of9,10-bis(phenylethynyl)anthracene. No clear differences were ob-served in the HOMO and LUMO pictures and transition dipolemoments between the models of 1 and 2, indicating that theinfluence of the methoxy groups is negligible. Given that theSmall 2024, 20, 2400063 © 2024 The Authors. Small published by Wiley-VCH GmbH2400063 (5 of 10) 16136829, 2024, 33, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/smll.202400063 by Cochrane Japan, Wiley Online Library on [15/08/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.small-journal.comwww.advancedsciencenews.com www.small-journal.comFigure 5. MD simulation snapshot of amphiphile 1 after 100 ns of equi-libration run. Solvent molecules are not shown for clarity. Yellow dottedlines represent intermolecular hydrogen bonds between amide groups.two amphiphiles form supramolecular fibers via linear hydrogenbonding, the stable dimer structures were optimized so that thecarbonyl groups of the amide face toward and outward from theanthracene group (Figure S9, Supporting Information). Consid-ering the direction of the dipole moments, both calculated ar-rangements of the luminophores result in a redshift of the ab-sorption bands of 1 and 2 when the supramolecular fibers formas conventional J-aggregates show.Molecular dynamics (MD) simulations were performed toinvestigate the molecular arrangement of the supramolecularfibers of 1. MD simulation with the initial structure of the dimerrevealed that the carbonyl groups of the amide facing the an-thracene group (Figures S9a and S10a, Supporting Informa-tion) became a uniform linear supramolecular fiber (Figure 5and Figure S11, Supporting Information). The average heightand width of the assembly fiber were estimated to be ≈1.8 and5 nm, respectively; these values are consistent with those ob-served in the AFM and TEM images (Figure 3a). Additionally,the direction of the continuously connected intermolecular hy-drogen bonds in the amide groups was parallel to the elongationdirection of the fibers. The distances of the anthracene groups be-tween neighboring molecules were found to be 0.45–0.5 nm, andfully overlapped 𝜋-stackings were not observed, suggesting thatthe molecules formed a J-aggregate-like arrangement. By con-trast, the molecular assembly obtained from the MD simulationwith the initial structure composed of the other type of dimer(Figures S9b and S10b, Supporting Information) indicated thatthe amide groups between neighboring molecules did not stablyform linear hydrogen bonds, and the molecular arrangement wasnonuniform (Figure S12, Supporting Information). The heightof the molecular assembly exceeded 2.5 nm and its width wasless than 3.5 nm. These values are distinct from those obtainedfrom the experimental results (Figure 3a). Amphiphile 2 alsoformed supramolecular fibers, with an arrangement of amidegroups similar to that in 1. The introduced TEG chains would al-ter the thermodynamically stable molecular arrangement, whichled to differences in the photophysical properties (Figure 2) andpeaks corresponding to the C═O bonds in the infrared spectra(Figure 4, top).Next, the mechanochromic luminescence of the supramolecu-lar fibers and their response upon the addition of water were in-Figure 6. External Stimuli-responsive luminescence of amphiphiles a) 1and b) 2. Scale bar: 5 mm. All photos were recorded with an excitationlight of 365 nm under dark conditions.vestigated (Figure 6). Neither of the supramolecular fibers weresoluble in water. Green fluorescence was observed in the solidsample of the supramolecular fiber composed of 1 under excita-tion at 365 nm, whereas amphiphile 2 in fibers exhibited yellow-green fluorescence. When mechanically ground, their fluores-cent colors turned yellow and orange, respectively. The grindingperformed here is very straightforward. After placing a solid sam-ple of 1 or 2 on a glass substrate, uniform grinding is performedwith a metal spatula, requiring no special equipment. The en-tire sample should be thoroughly ground to properly induce theconversion of the molecular assemblies, which will be discussedlater. Just pressing the solid sample results in little change inthe photoluminescence properties. Unexpectedly, the responsesof the ground samples significantly differed after the addition ofwater. The yellow emission of ground 1 was retained even afterdissolution in water. By contrast, the emission color of 2 changedfrom orange to green. The orange photoluminescence obtainedby grinding dry amphiphile 2 was not observed when compound2 was wetted and ground directly.Fluorescence spectroscopy was performed to confirm theemission color changes upon grinding and subsequent addi-tion of water (Figure 7). The initial solid supramolecular fibersof 1 and 2 displayed peaks at 529 and 552 nm, respectively, inaddition to shoulders due to their vibronic structure. Althoughthe emission intensity of the spectra at shorter wavelengthsdecreased because of self-absorption, monomer-like emission,similar to that recorded for solutions containing supramolecu-lar fibers, was observed for both initial solids. After grinding,both emission spectra exhibited significant redshifts and be-came broad and structureless (Figure 7). These spectral featuresFigure 7. Photoluminescence spectra of a) 1 and b) 2 in the initial solidstate (green), in the ground states (yellow), and in the water solution ofground samples (blue). All spectra were recorded with an excitation of385 nm.Small 2024, 20, 2400063 © 2024 The Authors. Small published by Wiley-VCH GmbH2400063 (6 of 10) 16136829, 2024, 33, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/smll.202400063 by Cochrane Japan, Wiley Online Library on [15/08/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.small-journal.comwww.advancedsciencenews.com www.small-journal.comFigure 8. Emission decay profiles of a) 1 and b) 2 in the initial solid state(green), in the ground states (yellow), and in the water solution of groundsamples (blue). The decay profiles of 1 were monitored at 565 nm (yel-low and blue lines) and 535 nm (green line). The decay profiles of 2 weremonitored at 600 nm (yellow line) and 560 nm (green and blue lines). Allprofiles were recorded with excitation light of 405 nm.indicate that the fluorophores formed excimers in the groundsamples. Similar static excimers were reported for several 9,10-bis(phenylethynyl)anthracene derivatives.[35–37] Furthermore, theaddition of water to ground 1 did not significantly change thefluorescence spectrum, indicating that the excimers were wellmaintained. Therefore, compound 1 forms molecular assembliesdifferent from those of the initial supramolecular fibers in wa-ter. The assembly of the luminophore in water was confirmed bythe absorption spectroscopic measurements (Figure S13a, Sup-porting Information). The absorption spectrum of the aqueoussolution of ground 1 is unambiguously red-shifted compared tothat of 1 in chloroform/methanol (1:1 v/v) (Figure 2a). These re-sults indicate that the fluorophores in water are arranged differ-ently from those in the supramolecular fibers (Figure S4a, Sup-porting Information). By contrast, in the case of 2, the additionof water caused a large blueshift in the fluorescence spectrum,with peaks observed at 523 and 549 nm (Figure 7b). This flu-orescence spectrum was similar to that of the water/methanolsolution in which the supramolecular fiber forms, thus suggest-ing that the excimer of the luminophore in 2 disappeared and themolecular assembly of the initial supramolecular fiber recovered.Indeed, the absorption spectrum of ground 2 in water was sim-ilar to that of the supramolecular fibers in a water/methanol so-lution (Figure S13b, Supporting Information), except for the un-ambiguous light-scattering effect. Ground 2 solved in the mixtureof water/methanol (7:3 v/v) also shows almost the same absorp-tion spectral shape between 400 and 550 nm as that of the initialsupramolecular fibers in the same solvent mixture. In additionto dissolution in water, exposure to water vapor also induces re-covery. Exposure of ground 2 to water vapor for 18 h shows a flu-orescence maximum at almost the same wavelength as the watersolution of ground 2 (Figure S14, Supporting Information).To gain further insights into the external stimulus-inducedchanges in the fluorescence of both amphiphiles, fluorescencelifetime measurements were performed (Figure 8; Table S1, Sup-porting Information). All decay profiles recorded for the solidsamples and water solutions of 1 and 2 were fitted with a tri-exponential decay function. The initial solid states of 1 and 2forming supramolecular fibers showed emission lifetimes be-tween 0.4 and 8.7 ns. After grinding, fluorescence decay becameslow for both compounds. Longer lifetimes of 43 and 42 ns wereobtained for ground 1 and 2 in the solid state, corresponding tothe excimer emission lifetime. Longer lifetimes have also beenreported for the excimers of 9,10-bis(phenylethynyl)anthracenederivatives.[35–37] A further slower decay was recorded after dis-solving ground 1 in water, and the longest lifetime of 60 ns wasobtained. By contrast, the water solution of ground 2 displayed adecay profile similar to that of 2 in the initial samples. The dataobtained from these time-resolved fluorescence measurementssupport our speculation that the excimer-forming arrangementof luminophores after the grinding of 1 was retained upon the ad-dition of water, whereas the initial supramolecular fiber arrange-ment recovered for 2 despite the significantly improved water sol-ubility of 2.Mechanical grinding and subsequent dissolution in water af-fected the hydrogen bonding modes of 1 and 2. As shown inFigure 4, peaks corresponding to the C=O stretching of amidegroups in 1 and 2 appeared at 1651 and 1643 cm−1 after grind-ing in the solid states, respectively. Therefore, almost all amidegroups were still involved in the formation of intermolecular hy-drogen bonds. However, the broad peaks suggest that the me-chanical grinding interfered with the linearly formed hydrogenbonds. After the addition of water to grounds 1 and 2, thin filmswere prepared by the evaporation of water under ambient con-ditions and were subjected to infrared measurements (Figure 4,bottom). The broad peak ascribed to C=O stretching was still ob-served for 1, indicating that the disordered structures inducedby grinding remained after the addition of water. Conversely,compound 2 exhibits a sharp peak similar to that of the initialsupramolecular fibers. This result also implies that the additionof water recovers the initial supramolecular fibers of 2.AFM and TEM observations were performed on 1 and 2 toclarify their assembled structures after the ground samples weredissolved in water. Several spherical structures with heights of≈4 nm were observed in the AFM images of the sample preparedfrom the aqueous solution of ground 1 (Figure 9a left; FigureS15, Supporting Information). The TEM images also showed nu-merous spheres with diameters between 1 and 3 nm (Figure 9aright; Figure S16, Supporting Information). These results indi-cate that compound 1 formed micellar assemblies (Figure S17,Supporting Information) after mechanical grinding and dissolu-tion in water. The micelles are assumed to be two-dimensionallyassembled into disk-like structures in the AFM images, whichis why a large difference in diameters was observed betweenthe AFM and TEM images. In the micelles, as excimer fluores-cence was observed, the luminophores formed 𝜋-stacked struc-tures. Given that the length between amide groups involved inhydrogen bonds is generally longer than the distance betweenaromatic groups forming 𝜋-stacking, a disordered hydrogen-bonding mode was adopted, thus resulting in the broadening ofthe C=O stretching peak observed in the IR spectrum (Figure 4).Similar micellar structures have been reported in previous stud-ies of dumbbell-shaped amphiphiles.[50] The micelle-like struc-ture was assumed to form when ground in the solid phase be-cause the emission spectra of ground 1 and water solution ofmicelles are almost identical. Small changes in the molecular ar-rangement should occur upon dissolution in water because theemission decay becomes slower (Figure 8a) and the shape of thepeak ascribed to C=O stretching in the IR spectrum changesslightly (Figure 4a). Because the dendritic structures were notwell-packed, the length of the micelles in the TEM image becameless than the molecular length.Small 2024, 20, 2400063 © 2024 The Authors. Small published by Wiley-VCH GmbH2400063 (7 of 10) 16136829, 2024, 33, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/smll.202400063 by Cochrane Japan, Wiley Online Library on [15/08/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.small-journal.comwww.advancedsciencenews.com www.small-journal.comFigure 9. AFM (left) and TEM (right) images of a) micelles consisting of 1 and b) fragmented supramolecular fibers of 2. The insets in the left panelsshow the height profiles of the micelles or supramolecular fibers. The insets in the right panels show magnified views of the areas enclosed by the dottedlines. The TEM images were taken without staining. The water solutions of ground 1 or 2 were used for both sample preparation.In contrast to the micelles of 1, fragmented fibrous molec-ular assemblies with a height of ≈2 nm were observed in theAFM images of the aqueous solution of ground 2 (Figure 9b left;Figure S18, Supporting Information). The lengths of the fibersbecame shorter than those of the initial supramolecular fibers.The TEM images also showed numerous fibers with a widthof 5 nm (Figure 9b right; Figure S19, Supporting Information).These height and width values coincide with those of the ini-tial supramolecular fibers consisting of 2 (Figure 3b; Figures S5and S6, Supporting Information). Considering the recovery ofthe fluorescence properties and the sharp peak attributed to C=Ostretching in the IR spectrum, the initial molecular assembly of2 should recover by the addition of water after grinding, althoughfragmentation occurred.The proposed changes in the molecular assemblies of 1 and2 in response to mechanical stimuli and the addition of waterare shown in Figure 1b. Initially, the amide groups of 1 and 2formed linear 1D hydrogen bonds. The fluorophores were placedin J-aggregate-like arrangements showing monomer-like fluo-rescence. In the assembled structures, hydrophilic dendrons donot prevent the formation of supramolecular fibers at the mi-crometer scale. In the supramolecular fiber of 1, the arrays ofhighly hydrophobic fluorophores are uncovered. Therefore, thehydrophilicity was not high, and supramolecular fibers formedin the chloroform-methanol mixture. By contrast, in the case of2, as the arrays of hydrophobic fluorophores were covered withTEG chains, the supramolecular fibers were highly hydrophilicand formed in the water-methanol mixture. When amphiphile 1in the solid consisting of the supramolecular fibers was ground,the supramolecular fibers were converted to micellar assem-blies in which the amide groups no longer formed the linearhydrogen bond, and fluorophores formed 𝜋-stacked structures.Consequently, ground 1 exhibited excimer emissions. In thisluminophore arrangement, moderately bulky hydrophilic den-drons prevented the compounds from forming 1D linear assem-blies. Compared with the initial J-aggregate-like arrangement of1, the fragmented array of the hydrophobic fluorophores in themicelles of 1 was surrounded by hydrophilic dendrons. There-fore, after the addition of water, the micellar assemblies wereretained because they were more thermodynamically stable inwater. This is the first example of supramolecular fibers beingconverted to micelles by mechanical stimuli, concomitant withemission color changes. The transition to micelles endowed 1with water solubility, although the initial supramolecular fiberswere insoluble in water. Owing to the molecular structural sim-ilarity between 1 and 2, amphiphile 2 is also expected to formmicellar structures after grinding, resulting in excimer emis-sion. This assumption is also supported by the fact that micellarSmall 2024, 20, 2400063 © 2024 The Authors. Small published by Wiley-VCH GmbH2400063 (8 of 10) 16136829, 2024, 33, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/smll.202400063 by Cochrane Japan, Wiley Online Library on [15/08/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.small-journal.comwww.advancedsciencenews.com www.small-journal.comstructures were observed in the AFM image taken for the sampleprepared with a water/methanol solution (3:7, v/v) of ground 2(Figure S20, Supporting Information). In the case of 2, the frag-mented supramolecular fibers were more stable than micellarassemblies in water because the hydrophobic arrays of the lu-minophores were covered with hydrophilic TEG groups. There-fore, the addition of water results in the conversion of micel-lar assemblies in the ground solid to fragmented supramolec-ular fibers in water, thus resulting in the recovery of the ini-tial emission properties. Consequently, the fragmentation of thesupramolecular fibers allowed them to dissolve in water. We as-sume that the significant difference in water solubility betweenthe initial supramolecular fibers of 2 and the fragmented fibersafter grinding is also ascribed to the inter-fiber interactions. Be-fore grinding, amphiphile 2 forms long supramolecular fibersand forms fiber bundles in which strong inter-fiber interactionsoccur. Therefore, amphiphile 2 cannot be dispersed in water. Af-ter grinding and the addition of water, the original molecular ar-rangements are restored. However, since the fragmented fibersare separated from each other and cannot form fiber bundles bybeing surrounded by water molecules, we speculate that the frag-mented fibers may dissolve in water.3. ConclusionIn summary, mechanochromic luminescent supramolecularfibers consisting of dumbbell-shaped amphiphiles 1 and 2 weresuccessfully developed. In the initial supramolecular fibers,the luminophore 9,10-bis(phenylethynyl)anthracene formed J-aggregate-like arrangements via linear hydrogen bonding be-tween the amide groups. Because the hydrogen-bonding modesin the fibers of 1 and 2 were slightly different, compound 2 ex-hibited a more pronounced redshift in the absorption spectrum.Both the compounds in the water-insoluble fibers became water-soluble after grinding in the solid state. When ground, the uni-form hydrogen bonds were disturbed, and linear supramolecularfibers were converted into micellar assemblies. In force-inducedmolecular assembled structures, the luminophores formed ex-cimers, thus leading to a significant redshift of the emissionspectra. As the micellar structures were favorable for 1 in wa-ter, the grinding-induced yellow fluorescence was retained af-ter the addition of water. Hydrophilic TEG chains introducedto the hydrophobic fluorophores of 2 stabilized the fragmentedsupramolecular fibers in water, thus resulting in the recovery ofthe initial fluorescence properties upon water addition.Mechanochromic fluorescent supramolecular fibers have asignificant advantage over conventional crystalline materials inthat they can be dispersed and supported on the surface of thematerial where the force is needed to be detected. Furthermore,as these fibers are only one molecule wide and uniform, theforce required to induce a fluorescent color change is constantand highly small. In the previous study on mechanochromic flu-orescent micelles in which fluorophore is 𝜋-stacked to exhibitexcimer emission, fluorescence color change was realized onlywhen all the arrangements of the fluorophores in the micellewere changed by force to ensure that no excimer sites existed.However, in supramolecular fibers, if only one excimer site is cre-ated by mechanical stimuli, energy transfer from the fluorophoreoccurs in the monomeric state, thus resulting in good sensi-tivity to forces. Furthermore, compared with mechanophores,which detect forces at the single-molecule level, supramolecu-lar fibers are advantageous in that they can detect forces at themesoscale without the need to introduce them into polymers orother materials. Currently, we are attempting to establish meth-ods to quantitatively evaluate mechanoresponsive luminescencefor supramolecular fibers under conditions in which they are dis-persed and supported by other materials.Supporting InformationSupporting Information is available from the Wiley Online Library or fromthe author.AcknowledgementsThe authors thank the Materials Analysis Division, Open Facility Center,Tokyo Institute of Technology, for the HRMS measurements. This work wassupported by JSPS KAKENHI (grant numbers JP23H04878, JP23H04874,and JP23H04879) in a Grant-in-Aid for Transformative Research Areas“Materials Science of Meso-Hierarchy.” This study was also supported bya Grant-in-Aid for Scientific Research on Innovative Areas “Aquatic Func-tional Materials” (grant numbers JP19H05718 and JP22H04531). Addi-tionally, it was supported by JSPS KAKENHI (grant number JP16K17885),JST CREST JPMJCR20B2, and the JGC-S SCHOLARSHIP FOUNDATION.Furthermore, this study was supported in part by the Multidisciplinary Co-operative Research Program of the Center for Computational Sciences atthe University of Tsukuba. Some of the computations were performed us-ing computer facilities at the Research Institute for Information Technol-ogy, Kyushu University, and the Research Center for Computational Sci-ence, Okazaki, Japan (Project: 23-IMS-C038 and 23-IMS-C109).Conflict of InterestThe authors declare no conflict of interest.Data Availability StatementThe data that support the findings of this study are available in the sup-plementary material of this article.Keywordsamphiphiles, grinding-induced water solubility, J-aggregation,mechanochromic luminescence, micelles, supramolecular polymersReceived: January 3, 2024Revised: February 28, 2024Published online: March 10, 2024[1] Y. Sagara, S. Yamane, M. Mitani, C. Weder, T. Kato, Adv. Mater. 2016,28, 1073.[2] Y. Sagara, T. Kato, Nat. Chem. 2009, 1, 605.[3] Z. Chi, X. Zhang, B. Xu, X. Zhou, C. Ma, Y. Zhang, S. Liu, J. Xu, Chem.Soc. Rev. 2012, 41, 3878.[4] Z. Ma, Z. Wang, M. Teng, Z. Xu, X. Jia, ChemPhysChem 2015, 16, 1811.[5] S. Ito, J. Photochem. Photobiol. 2022, 51, 100481.Small 2024, 20, 2400063 © 2024 The Authors. Small published by Wiley-VCH GmbH2400063 (9 of 10) 16136829, 2024, 33, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/smll.202400063 by Cochrane Japan, Wiley Online Library on [15/08/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.small-journal.comwww.advancedsciencenews.com www.small-journal.com[6] S. Ito, CrystEngComm 2022, 24, 1112.[7] S. Ito, Chem. Lett. 2021, 50, 649.[8] Y. Sagara, T. Mutai, I. Yoshikawa, K. Araki, J. Am. Chem. Soc. 2007,129, 1520.[9] J. Kunzelman, M. Kinami, B. R. Crenshaw, J. D. Protasiewicz, C.Weder, Adv. Mater. 2008, 20, 119.[10] Y. Sagara, T. Kato, Angew. Chem. Int. Ed. 2008, 47, 5175.[11] Y. Ooyama, Y. Kagawa, H. Fukuoka, G. Ito, Y. Harima, Eur. J. Org.Chem. 2009, 5321.[12] S.-J. Yoon, J. W. Chung, J. Gierschner, K. S. Kim, M.-G. Choi, D. Kim,S. Y. Park, J. Am. Chem. Soc. 2010, 132, 13675.[13] Y. Ooyama, G. Ito, H. Fukuoka, T. Nagano, Y. Kagawa, I. Imae, K.Komaguchi, Y. Harima, Tetrahedron 2010, 66, 7268.[14] Y. Sagara, T. Kato, Angew. Chem. Int. Ed. 2011, 50, 9128.[15] X. Luo, J. Li, C. Li, L. Heng, Y. Q. Dong, Z. Liu, Z. Bo, B. Z. Tang, Adv.Mater. 2011, 23, 3261.[16] H. Li, X. Zhang, Z. Chi, B. Xu, W. Zhou, S. Liu, Y. Zhang, J. Xu, Org.Lett. 2011, 13, 556.[17] M. J. Teng, X. R. Jia, X. F. Chen, Y. Wei, Angew. Chem. Int. Ed. 2012,51, 6398.[18] M. S. Kwon, J. Gierschner, S. J. Yoon, S. Y. Park, Adv. Mater. 2012, 24,5487.[19] X. Gu, J. Yao, G. Zhang, Y. Yan, C. Zhang, Q. Peng, Q. Liao, Y. Wu, Z.Xu, Y. Zhao, H. Fu, D. Zhang, Adv. Funct. Mater. 2012, 22, 4862.[20] Y. Dong, B. Xu, J. Zhang, X. Tan, L. Wang, J. Chen, H. Lv, S. Wen, B.Li, L. Ye, B. Zou, W. Tian, Angew. Chem. Int. Ed. 2012, 51, 10782.[21] N. Mizoshita, T. Tani, S. Inagaki, Adv. Mater. 2012, 24, 3350.[22] J. Wang, J. Mei, R. Hu, J. Z. Sun, A. Qin, B. Z. Tang, J. Am. Chem. Soc.2012, 134, 9956.[23] K. Nagura, S. Saito, H. Yusa, H. Yamawaki, H. Fujihisa, H. Sato, Y.Shimoikeda, S. Yamaguchi, J. Am. Chem. Soc. 2013, 135, 10322.[24] W. Z. Yuan, Y. Tan, Y. Gong, P. Lu, J. W. Lam, X. Y. Shen, C. Feng, H. H.Sung, Y. Lu, I. D. Williams, J. Z. Sun, Y. Zhang, B. Z. Tang, Adv. Mater.2013, 25, 2837.[25] M.-S. Yuan, D.-E. Wang, P. Xue, W. Wang, J.-C. Wang, Q. Tu, Z. Liu, Y.Liu, Y. Zhang, J. Wang, Chem. Mater. 2014, 26, 2467.[26] H. J. Kim, D. R. Whang, J. Gierschner, C. H. Lee, S. Y. Park, Angew.Chem. Int. Ed. 2015, 54, 4330.[27] L. Wang, K. Wang, B. Zou, K. Ye, H. Zhang, Y. Wang, Adv. Mater. 2015,27, 2918.[28] Y. Sagara, Y. C. Simon, N. Tamaoki, C. Weder, Chem. Commun. 2016,52, 5694.[29] Z. Ma, Z. Wang, X. Meng, Z. Ma, Z. Xu, Y. Ma, X. Jia, Angew. Chem.Int. Ed. 2016, 55, 519.[30] S. K. Park, I. Cho, J. Gierschner, J. H. Kim, J. H. Kim, J. E. Kwon, O. K.Kwon, D. R. Whang, J.-H. Park, B.-K. An, S. Y. Park, Angew. Chem. Int.Ed. 2016, 55, 203.[31] M. Okazaki, Y. Takeda, P. Data, P. Pander, H. Higginbotham, A. P.Monkman, S. Minakata, Chem. Sci. 2017, 8, 2677.[32] Y. Sagara, K. Kubo, T. Nakamura, N. Tamaoki, C. Weder, Chem. Mater.2017, 29, 1273.[33] Y. Sagara, C. Weder, N. Tamaoki, Chem. Mater. 2017, 29, 6145.[34] A. Lavrenova, D. W. Balkenende, Y. Sagara, S. Schrettl, Y. C. Simon,C. Weder, J. Am. Chem. Soc. 2017, 139, 4302.[35] Y. Sagara, K. Takahashi, T. Nakamura, N. Tamaoki, Chem. Asian J.2020, 15, 478.[36] Y. Sagara, K. Takahashi, T. Nakamura, N. Tamaoki, J. Mater. Chem. C2020, 8, 10039.[37] Y. Sagara, K. Takahashi, A. Seki, T. Muramatsu, T. Nakamura, N.Tamaoki, J. Mater. Chem. C 2021, 9, 1671.[38] H. Ito, T. Saito, N. Oshima, N. Kitamura, S. Ishizaka, Y. Hinatsu, M.Wakeshima, M. Kato, K. Tsuge, M. Sawamura, J. Am. Chem. Soc. 2008,130, 10044.[39] V. N. Kozhevnikov, B. Donnio, D. W. Bruce, Angew. Chem. Int. Ed.2008, 47, 6286.[40] H. Ito, M. Muromoto, S. Kurenuma, S. Ishizaka, N. Kitamura, H.Sato, T. Seki, Nat. Commun. 2013, 4, 2009.[41] Q. Benito, X. F. Le Goff, S. Maron, A. Fargues, A. Garcia, C. Martineau,F. Taulelle, S. Kahlal, T. Gacoin, J. P. Boilot, S. Perruchas, J. Am. Chem.Soc. 2014, 136, 11311.[42] H. Sun, S. Liu, W. Lin, K. Y. Zhang, W. Lv, X. Huang, F. Huo, H. Yang,G. Jenkins, Q. Zhao, W. Huang, Nat. Commun. 2014, 5, 3601.[43] T. Seki, Y. Takamatsu, H. Ito, J. Am. Chem. Soc. 2016, 138, 6252.[44] B. Huitorel, Q. Benito, A. Fargues, A. Garcia, T. Gacoin, J.-P. Boilot, S.Perruchas, F. Camerel, Chem. Mater. 2016, 28, 8190.[45] T. Seki, N. Tokodai, S. Omagari, T. Nakanishi, Y. Hasegawa, T. Iwasa,T. Taketsugu, H. Ito, J. Am. Chem. Soc. 2017, 139, 6514.[46] M. Jin, T. Seki, H. Ito, J. Am. Chem. Soc. 2017, 139, 7452.[47] Y. Ren, W. H. Kan, V. Thangadurai, T. Baumgartner, Angew. Chem. Int.Ed. 2012, 51, 3964.[48] Y. Sagara, T. Komatsu, T. Ueno, K. Hanaoka, T. Kato, T. Nagano, Adv.Funct. Mater. 2013, 23, 5277.[49] S. Yagai, S. Okamura, Y. Nakano, M. Yamauchi, K. Kishikawa, T.Karatsu, A. Kitamura, A. Ueno, D. Kuzuhara, H. Yamada, T. Seki, H.Ito, Nat. Commun. 2014, 5, 4013.[50] Y. Sagara, T. Komatsu, T. Ueno, K. Hanaoka, T. Kato, T. Nagano, J. Am.Chem. Soc. 2014, 136, 4273.[51] Y. Sagara, T. Komatsu, T. Terai, T. Ueno, K. Hanaoka, T. Kato, T.Nagano, Chem. Eur. J. 2014, 20, 10397.[52] C. Liang, M. Li, Y. Chen, ACS Appl. Mater. Interfaces 2021, 13, 20698.[53] Y. Chen, A. Li, X. Li, L. Tu, Y. Xie, S. Xu, Z. Li, Adv. Mater. 2023, 35,2211917.[54] J. H. Ryu, D. J. Hong, M. Lee, Chem. Commun. 2008, 1043.[55] X. Zhang, S. Rehm, M. M. Safont-Sempere, F. Würthner, Nat. Chem.2009, 1, 623.[56] Y. B. Lim, K. S. Moon, M. Lee, Chem. Soc. Rev. 2009, 38, 925.[57] T. Heek, C. Fasting, C. Rest, X. Zhang, F. Wurthner, R. Haag, Chem.Commun. 2010, 46, 1884.[58] H.-J. Kim, T. Kim, M. Lee, Acc. Chem. Res. 2011, 44, 72.[59] B. N. Thota, L. H. Urner, R. Haag, Chem. Rev. 2016, 116, 2079.[60] Y. Sagara, M. Karman, E. Verde-Sesto, K. Matsuo, Y. Kim, N. Tamaoki,C. Weder, J. Am. Chem. Soc. 2018, 140, 1584.[61] Y. Sagara, M. Karman, A. Seki, M. Pannipara, N. Tamaoki, C. Weder,ACS Cent. Sci. 2019, 5, 874.[62] Y. Sagara, H. Traeger, J. Li, Y. Okado, S. Schrettl, N. Tamaoki, C.Weder, J. Am. Chem. Soc. 2021, 143, 5519.[63] T. Muramatsu, Y. Okado, H. Traeger, S. Schrettl, N. Tamaoki, C.Weder, Y. Sagara, J. Am. Chem. Soc. 2021, 143, 9884.[64] H. Traeger, Y. Sagara, D. J. Kiebala, S. Schrettl, C. Weder, Angew.Chem. Int. Ed. 2021, 60, 16191.[65] S. Thazhathethil, T. Muramatsu, N. Tamaoki, C. Weder, Y. Sagara,Angew. Chem. Int. Ed. 2022, 61, 202209225.[66] S. Shimizu, H. Yoshida, K. Mayumi, H. Ajiro, Y. Sagara, Mater. Chem.Front. 2023, 7, 4073.[67] T. Muramatsu, S. Shimizu, J. M. Clough, C. Weder, Y. Sagara, ACSAppl. Mater. Interfaces 2023, 15, 8502.[68] K. Hiratsuka, T. Muramatsu, T. Seki, C. Weder, G. Watanabe, Y.Sagara, J. Mater. Chem. C 2023, 11, 3949.[69] M. Lübtow, I. Helmers, V. Stepanenko, R. Q. Albuquerque, T. B.Marder, G. Fernández, Chem. Eur. J. 2017, 23, 6198.[70] M. Levitus, M. A. Garcia-Garibay, J. Phys. Chem. A 2000, 104,8632.[71] F. Würthner, T. E. Kaiser, C. R. Saha-Möller, Angew. Chem. Int. Ed.2011, 50, 3376.[72] T. E. Kaiser, V. Stepanenko, F. Würthner, J. Am. Chem. Soc. 2009, 131,6719.Small 2024, 20, 2400063 © 2024 The Authors. Small published by Wiley-VCH GmbH2400063 (10 of 10) 16136829, 2024, 33, Downloaded from https://onlinelibrary.wiley.com/doi/10.1002/smll.202400063 by Cochrane Japan, Wiley Online Library on [15/08/2024]. See the Terms and Conditions (https://onlinelibrary.wiley.com/terms-and-conditions) on Wiley Online Library for rules of use; OA articles are governed by the applicable Creative Commons Licensehttp://www.advancedsciencenews.comhttp://www.small-journal.com Grinding-Induced Water Solubility Exhibited by Mechanochromic Luminescent Supramolecular Fibers 1. Introduction 2. Results and Discussion 3. Conclusion Supporting Information Acknowledgements Conflict of Interest Data Availability Statement Keywords