Mechanically Responsive Luminescent Polymers Based on Supramolecular Cyclophane Mechanophores
- 30 March 2021
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 143 (14), 5519-5525
- https://doi.org/10.1021/jacs.1c01328
Abstract
A new approach to cyclophane-based supramolecular mechanophores is presented. We report a mechanically responsive cyclic motif that contains two fluorescent 1,6-bis(phenylethynyl)pyrene moieties that are capable of forming intramolecular excimers. The emission spectra of dilute solutions of this cyclophane and a polyurethane elastomer into which a small amount of the mechanophore (0.08 wt %) had been covalently integrated are dominated by excimer emission. Films of the cyclophane-containing polyurethane also display a considerable portion of excimer emission, but upon deformation, the fluorescence becomes monomer-dominated and a perceptible change from cyan to blue is observed. The response is instant, reversible, and consistent with a mechanically induced change of the molecular conformation of the mechanophore so that the excimer-promoting interactions between the luminophores are suppressed. In-depth investigations show a correlation between the applied strain and the emission color, which can conveniently be expressed by the ratio of monomer to excimer emission intensity. The current study suggests that cyclophanes can be utilized to develop various supramolecular mechanophores that detect and visualize weak forces occurring in polymeric materials or generated by living tissues.Funding Information
- Schweizerischer Nationalfonds zur F?rderung der Wissenschaftlichen Forschung
- Adolphe Merkle Foundation
- Precursory Research for Embryonic Science and Technology (JPMJPR17P6)
- Japan Society for the Promotion of Science (JP18H02024, JP20H05198)
- China Scholarship Council (201806935036)
- Dynamic Alliance for Open Innovation Bridging Human, Environment and Materials
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