Light-triggered thermal conductivity switching in azobenzene polymers

Area of Science:

• Materials Science
• Polymer Chemistry
• Condensed Matter Physics

Background:

• Controlling thermal conductivity in materials is crucial for advanced energy applications.
• Developing stimuli-responsive materials with tunable thermophysical properties remains a significant challenge.

Purpose of the Study:

• To engineer a polymer capable of reversible switching between distinct thermal conductivity states.
• To investigate the mechanism behind light-induced modulation of thermal properties in polymers.

Main Methods:

• Utilized in situ time-domain thermoreflectance (TDTR) for thermal conductivity measurements.
• Employed in situ synchrotron X-ray scattering to probe structural changes.
• Investigated light-induced conformational transitions in azobenzene polymers using UV and green light.

Main Results:

• Achieved a threefold change in thermal conductivity, from 0.10 W m^-1 K^-1 (low) to 0.35 W m^-1 K^-1 (high).
• Demonstrated reversible switching between states triggered by UV and green light illumination.
• Linked thermal conductivity changes to light-induced modulation of chain alignment and π-π stacking via azobenzene conformational changes.

Conclusions:

• Developed a novel light-responsive azobenzene polymer with switchable thermal conductivity.
• Established a mechanism for controlling thermophysical properties by light-induced modulation of interchain π-π networks.
• The reversible crystal-to-liquid transition occurs rapidly at room temperature, offering practical potential.