Mechanochemical Fluorescence Switching in Polymers Containing Dithiomaleimide Moieties

Area of Science:

• Polymer Chemistry
• Materials Science
• Mechanochemistry

Background:

• Polymers exhibiting mechanochemical responses, particularly changes in fluorescence, are of significant scientific interest.
• Mechanofluorophores are materials that change their fluorescence properties upon mechanical stress.
• Developing new mechanofluorophores is crucial for advancing smart materials and sensors.

Purpose of the Study:

• To introduce and investigate the dithiomaleimide (DTM) motif as a novel mechanofluorophore.
• To synthesize and characterize polymers incorporating the DTM motif.
• To evaluate the mechanochemical response, specifically fluorescence changes, of these DTM-containing polymers.

Main Methods:

• Synthesis of poly(methyl acrylate) (PMA-DTM) and poly(ε-caprolactone) (PCL-DTM) using bifunctional DTM-containing initiators.
• Controlled radical polymerization and coordination-insertion ring-opening polymerization techniques were employed.
• Ultrasonic treatment was used to induce mechanical stress on the synthesized polymers.
• Fluorescence intensity and molecular weight changes were monitored during mechanical treatment.

Main Results:

• Polymers containing the dithiomaleimide (DTM) motif exhibited a mechanically induced fluorescence turn-off.
• Both molecular weight and fluorescence intensity decreased with similar kinetics upon ultrasonic treatment for PMA-DTM and PCL-DTM.
• No significant fluorescence changes were observed in DTM-free reference polymers, confirming the role of the DTM motif.
• The observed mechanoresponse was dependent on the initial molecular weight of the polymers.

Conclusions:

• The dithiomaleimide (DTM) motif effectively functions as a mechanophore.
• Mechanical stress leads to a decrease in fluorescence intensity in DTM-containing polymers.
• This study demonstrates a new class of mechanofluorophores with potential applications in stress-sensing materials.