Light-triggered thermal conductivity switching in azobenzene polymers.
basic_science · Level V
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- Record sourced from PubMed, PMID 30850519.
- Also identified by DOI 10.1073/pnas.1817082116 and PMC identifier 6442584.
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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<sup>-1</sup> K<sup>-1</sup>) and low thermal conductivity (0.10 W m<sup>-1</sup> K<sup>-1</sup>) states. This threefold change in the thermal conductivity is achieved by modulation of chain alignment resulted from the conformational transition between planar (<i>trans</i>) and nonplanar (<i>cis</i>) 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.