Azobenzene as a photoswitchable mechanophore

Area of Science:

• Materials Science
• Polymer Chemistry
• Physical Chemistry

Background:

• Azobenzene is a well-known photoresponsive molecule used in materials science.
• Previous research explored force-induced isomerization, but the effect of force on azobenzene rupture remained uninvestigated.

Purpose of the Study:

• To investigate the effect of light-induced structural changes on the rupture forces of azobenzene.
• To explore azobenzene as a light-responsive mechanophore for controlling material properties.

Main Methods:

• Single-molecule force spectroscopy
• Ultrasonication
• Dynamic force spectroscopy
• Quantum-chemical calculations

Main Results:

• Cis and trans para-azobenzene isomers exhibit distinct mechanical properties and rupture forces.
• Rupture force differences are attributed to the pulling direction, not isomeric energy differences.
• Light-induced conformational changes of azobenzene alter its rupture forces.

Conclusions:

• Azobenzene's mechanical properties can be modulated by light, making it a light-responsive mechanophore.
• These findings enable rational control over the macroscopic fracture behavior of polymer networks via photoillumination.
• This work presents a novel approach for engineering polymer networks with light-regulatable mechanical properties.