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Updated: Jan 28, 2026

Measuring Light-Switching Behavior Using an Occupancy and Light Data Logger
Published on: January 16, 2020
Light-triggered thermal conductivity switching in azobenzene polymers
Jungwoo Shin1,2, Jaeuk Sung1,2,3, Minjee Kang1,2
1Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, IL 61801.
Abstract:
Materials that can be switched between low and high thermal conductivity states would advance the control and conversion of thermal energy. Employing in situ time-domain thermoreflectance (TDTR) and in situ synchrotron X-ray scattering, we report a reversible, light-responsive azobenzene polymer that switches between high (0.35 W m-1 K-1) and low thermal conductivity (0.10 W m-1 K-1) states. This threefold change in the thermal conductivity is achieved by modulation of chain alignment resulted from the conformational transition between planar (trans) and nonplanar (cis) azobenzene groups under UV and green light illumination. This conformational transition leads to changes in the π-π stacking geometry and drives the crystal-to-liquid transition, which is fully reversible and occurs on a time scale of tens of seconds at room temperature. This result demonstrates an effective control of the thermophysical properties of polymers by modulating interchain π-π networks by light.
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