A near-infrared light-driven composite for smart and robust adhesion based on dynamic photochemistry

Area of Science:

• Materials Science
• Polymer Chemistry
• Nanotechnology

Background:

• Azobenzene-containing liquid-crystalline polymers offer phototunable properties for various applications.
• Simultaneous trans and cis isomer dynamics and NIR light control remain challenging experimental areas.

Purpose of the Study:

• To develop an environmentally friendly, NIR light-driven photoresponsive and reusable adhesive.
• To investigate the dynamic equilibrium of azobenzene isomers under NIR irradiation.
• To explore the potential of combining upconversion nanoparticles with azobenzene polymers.

Main Methods:

• Integration of UV/blue-emitting upconversion nanoparticles (UCNPs) with siloxane main-chain azobenzene photoswitches.
• Utilizing near-infrared (NIR) light for photoactuation and simultaneous bicolor emissions.
• Numerical and experimental analysis of trans-cis isomerization dynamics and material property changes.

Main Results:

• Achieved NIR light-driven photoresponsiveness and reusability in a novel adhesive composite.
• Demonstrated dynamic equilibrium of azobenzene isomers under varying NIR power.
• Observed significant decreases in elasticity and viscosity under high-power NIR, linked to free volume expansion and structural changes.
• Showcased robust switching of adhesion strength over six cycles.

Conclusions:

• The developed UCNP-azobenzene composite exhibits significant potential as a NIR photoresponsive material.
• Modulating NIR excitation power allows for control over isomer dynamics and material properties.
• This approach overcomes limitations of UV/visible light actuation and offers advanced functionalities.