Rotaxane-Based Dual Function Mechanophores Exhibiting Reversible and Irreversible Responses
Tatsuya Muramatsu1, Yuji Okado2, Hanna Traeger3
1Department of Materials Science and Engineering, Tokyo Institute of Technology, 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8552, Japan.
Journal of the American Chemical Society
|June 24, 2021
Summary
New rotaxane mechanophores offer dual optical signals for polymers. These materials show reversible fluorescence changes with mechanical stress and irreversible changes upon high force, enabling damage monitoring.
Area of Science:
- Supramolecular Chemistry
- Polymer Science
- Materials Science
Background:
- Mechanochromic mechanophores enable polymers to signal mechanical events optically.
- Rotaxanes are mechanically interlocked molecules with potential for designing advanced materials.
Purpose of the Study:
- To develop novel rotaxane-based supramolecular mechanophores exhibiting both reversible and irreversible fluorescence changes.
- To investigate the relationship between molecular structure, mechanical force, and optical response in polymers.
Main Methods:
- Synthesis of rotaxane mechanophores featuring a luminophore-carrying ring and a quencher on an axle.
- Incorporation of these rotaxanes into polyurethane (PU) elastomers.
- Mechanical testing of the elastomers to evaluate fluorescence response under varying force and strain conditions.
Main Results:
- Rotaxane mechanophores demonstrated reversible fluorescence switching via molecular shuttling under moderate force.
- Irreversible fluorescence changes and permanent optical signals were observed upon high force, leading to ring dethreading and mechanical bond breakage.
- Polyurethane elastomers containing these mechanophores showed distinct reversible and irreversible optical responses corresponding to applied mechanical stimuli.
Conclusions:
- Rotaxane-based supramolecular mechanophores can be designed to provide dual, force-dependent optical readouts (reversible and irreversible).
- The molecular design, specifically the choice of ring and stopper moieties, is critical for achieving this dual response.
- These materials offer a pathway for real-time monitoring of polymer deformation and a record of past mechanical damage through optical signals.
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