Mechanoresponsive Behavior of a Polymer-Embedded Red-Light Emitting Rotaxane Mechanophore

Muramatsu, Tatsuya; Sagara, Yasuyuki; Traeger, Hanna; Tamaoki, Nobuyuki; Weder, Christoph

doi:10.1021/acsami.9b06302

Cited by 53 publications

(87 citation statements)

References 42 publications

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“…[ 149 ] Further exploring their utility, polymers were prepared in which the dye separation in the pristine, rotaxane‐bearing PU leads to a trapped state. [ 150 ] Thus, a cyclophane‐based macrocycle was threaded onto a dumbbell with a BODIPY dye to furnish a red‐light emitting rotaxane. Covalently embedding the latter into a PU matrix caused the rotaxane to remain in a trapped state in which the fluorophore and quencher moieties were separated.…”

Section: Mechanical Stimulation Of Hetero‐molecular Complexesmentioning

confidence: 99%

From Molecules to Polymers—Harnessing Inter‐ and Intramolecular Interactions to Create Mechanochromic Materials

Traeger

Kiebala

Weder

et al. 2020

Macromol. Rapid Commun.

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tion occurs to avoid catastrophic materials failure and to possibly redirect degradation processes into useful responses. Consequently, research efforts directed toward the investigation and development of mechanoresponsive materials has drawn ever increasing attention. [2,3,5-8] Polymers that translate mechanical stresses into a defined response are thought to be useful for many different applications, including as tamper-proof packaging materials, [9] as degradable plastics, [10,11] or for structural health monitoring. [12] One possibility to render polymers mechanoresponsive is the integration of so-called mechanophores. The latter generally feature a weak covalent bond that undergoes either homo-or heterolytic cleavage upon experiencing a force that exceeds a certain threshold. [1,5,7,13,14] These motifs are covalently incorporated into a polymer and serve as predefined weak links that preferentially break or transform in response to an applied mechanical force. [1,6,14-16] Widely investigated mechanophores include spiropyrans, 1,2-dioxetanes, and Diels-Alder adducts. [16-18] The rate constants, threshold forces, and transition state bond-lengths and energies of many mechanophores have been well-characterized via techniques such as single-molecule force spectroscopy (SMFS), [19-22] force-modified potential energy surface modeling, [23] and in situ activation using sonication. [2,22,24] The insights gained in such studies have driven advancements in the field of mechanoresponsive materials and the mechanical activation has, for example, been harnessed to promote thermodynamically unfavorable reactions, [19] affect the intra-or intermolecular transfer of protons, [20,25,26] release small molecules, [27] initiate the depolymerization of the surrounding material, [10,28] or elicit changes in the material's color or fluorescence. [16,17,29] The fact that the active bond or functional group of a mechanophore is typically cleaved irreversibly can limit its utility. Some mechanophores can be returned to their original state through an additional stimulus such as light or heat, but unless the mechanophore undergoes a nonscissile cleavage (e.g., a ring-opening reaction, such as in spiropyrans), the reversal is generally hampered by kinetic factors that leave the mechanophore in its cleaved state. [30] An irreversible response can be desirable for some

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Section: Mechanical Stimulation Of Hetero‐molecular Complexesmentioning

confidence: 99%

From Molecules to Polymers—Harnessing Inter‐ and Intramolecular Interactions to Create Mechanochromic Materials

Traeger

Kiebala

Weder

et al. 2020

Macromol. Rapid Commun.

Self Cite

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“…However, the exact force acting on a mechanophore is difficult to ascertain, as many factors during cavitation or within a material influence the transmittance of the force to the mechanophore, such as the molecules overall rigidity, [3f,9] the length of attached residues [10] or the material's morphology [11] . Thus, recent activities on metallocenes, [7] Cu‐pyridine, [12] and B−N bonds [13] demonstrated metal/ligand‐cleavage in polymeric bulk‐systems or in solution, which finally did not allow for a precise, direct quantification of the individual metal/ligand‐bond upon mechanical stressing.…”

Section: Introductionmentioning

confidence: 99%

Activation of a Copper Biscarbene Mechano‐Catalyst Using Single‐Molecule Force Spectroscopy Supported by Quantum Chemical Calculations

Sammon

Biewend

Michael

et al. 2021

Chemistry A European J

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Single‐molecule force spectroscopy allows investigation of the effect of mechanical force on individual bonds. By determining the forces necessary to sufficiently activate bonds to trigger dissociation, it is possible to predict the behavior of mechanophores. The force necessary to activate a copper biscarbene mechano‐catalyst intended for self‐healing materials was measured. By using a safety line bypassing the mechanophore, it was possible to pinpoint the dissociation of the investigated bond and determine rupture forces to range from 1.6 to 2.6 nN at room temperature in dimethyl sulfoxide. The average length‐increase upon rupture of the Cu−C bond, due to the stretching of the safety line, agrees with quantum chemical calculations, but the values exhibit an unusual scattering. This scattering was assigned to the conformational flexibility of the mechanophore, which includes formation of a threaded structure and recoiling of the safety line.

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“…[22][23][24][25][26][27][28] Among these, particularly attractive are mechanophores that do not require scission of covalent bonds for the activation and change of their properties. [29][30][31][32][33] In the case of rotaxanes, the activation process does not involve any bond cleavage, leading to a low activation energy of the process. [30] In the study reported herein, we extensively investigated the vase-kite switching of tetraquinoxaline cavitands in polymers through the application of tensile strain.…”

Section: Introductionmentioning

confidence: 99%

“…Over the past few years, thanks to the progress in mechanophore design, a broad range of mechanically‐triggered transformations was attained . Among these, particularly attractive are mechanophores that do not require scission of covalent bonds for the activation and change of their properties . In the case of rotaxanes, the activation process does not involve any bond cleavage, leading to a low activation energy of the process …”

Section: Introductionmentioning

confidence: 99%

Mechanically‐Driven Vase–Kite Conformational Switch in Cavitand Cross‐Linked Polyurethanes

et al. 2020

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The eligibility of tetraquinoxaline cavitands (QxCav) as molecular grippers relies on their unique conformational mobility between a closed (vase) and an open (kite) form, triggered in solution by conventional stimuli like pH, temperature and ion concentration. In the present paper, the mechanochemical conformational switching of ad hoc functionalized QxCav covalently embedded in an elastomeric polydimethylsiloxane and in a more rigid polyurethane matrix is investigated. The rigid polymer matrix is more effective in converting mechanical force into a conformational switch at the molecular level, provided that all four quinoxaline wings are covalently connected to the polymer.

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Mechanoresponsive Behavior of a Polymer-Embedded Red-Light Emitting Rotaxane Mechanophore

Cited by 53 publications

References 42 publications

From Molecules to Polymers—Harnessing Inter‐ and Intramolecular Interactions to Create Mechanochromic Materials

From Molecules to Polymers—Harnessing Inter‐ and Intramolecular Interactions to Create Mechanochromic Materials

Activation of a Copper Biscarbene Mechano‐Catalyst Using Single‐Molecule Force Spectroscopy Supported by Quantum Chemical Calculations

Mechanically‐Driven Vase–Kite Conformational Switch in Cavitand Cross‐Linked Polyurethanes

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