Force-Induced Near-Infrared Chromism of Mechanophore-Linked Polymers

Area of Science:

• Polymer Science
• Materials Chemistry
• Spectroscopy

Background:

• Mechanophores are molecules that undergo a chemical or physical change in response to mechanical force.
• Near-infrared (NIR) chromism involves a change in color or absorption in the NIR region upon stimulation.
• Developing NIR mechanochromic polymers is crucial for advanced sensing and imaging applications.

Purpose of the Study:

• To develop and integrate a novel NIR mechanophore into a polymer chain.
• To demonstrate the first instance of force-induced NIR chromism in polymeric materials.
• To explore the potential applications of these NIR mechanochromic polymers.

Main Methods:

• Synthesis of a novel benzo[1,3]oxazine (OX) fused with a heptamethine cyanine moiety as the NIR mechanophore.
• Incorporation of the mechanophore into a poly(methyl acrylate) polymer chain.
• Characterization using UV-vis-NIR absorption/fluorescence spectroscopies, gel permeation chromatography (GPC), NMR, and DFT simulations.

Main Results:

• The developed mechanophore exhibited NIR mechanochromism in solution, thin-film, and bulk polymer states.
• Mechanochemical activity was confirmed through various spectroscopic and analytical techniques.
• Successful integration into poly(methyl acrylate) demonstrated polymer-based NIR mechanochromism.

Conclusions:

• The study presents the first force-induced NIR chromism in polymeric materials using a novel OX-cyanine mechanophore.
• NIR mechanochromic polymers show significant promise for applications in mechanical force sensing and damage detection.
• Potential applications extend to bioimaging and biomechanics due to the NIR properties.