Light-triggered thermal conductivity switching in azobenzene polymers

Jungwoo Shin, Jaeuk Sung, Minjee Kang, Xu Xie, Byeongdu Lee, Kyung Min Lee, Timothy J. White, Cecilia Leal, Nancy R. Sottos, Paul V. Braun, David G. Cahill

Research output: Contribution to journalArticle

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.

Original languageEnglish (US)
Pages (from-to)5973-5978
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume116
Issue number13
DOIs
StatePublished - Jan 1 2019

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Keywords

  • Azobenzene
  • Phase transition
  • Polymer
  • Thermal conductivity
  • Thermal switch

ASJC Scopus subject areas

  • General

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