Thermal conductivity switching of side-chain azobenzene polymer films by photo-triggered reversible crystalline lamellar formation

ORAL

Abstract

We study the structural and thermal properties of side-chain azobenzene polymer films via in-situ synchrotron X-ray scattering and in-situ time-domain thermoreflectance (TDTR). The spin-coated side-chain azobenzene polymer films show vertically aligned azobenzene substituents on Al surface. We found that the increase in number of repeating units of side-chain azobenzene polymers results in transition from disordered 2-D structure to highly ordered crystalline lamellar structure with increasing out-of-plane thermal conductivity from 0.2 to 0.35 W m-1 K-1. In addition, we observed that ultraviolet (UV) light drives trans-to-cis photoisomerization of azobenzene substituents, resulting in isotropic liquid states with thermal conductivity of 0.1-0.15 W m-1K-1 while visible light completely restores the crystalline lamellar structure. We attribute the out-of-plane thermal conductivity switching of azobenzene side-chain polymer film to the tunable molecular thermal pathwaycontrolled by number of repeating units and conformation changes driven by light.

*This work is funded by the National Science Foundation Engineering Research Center for Power Optimization of Electro Thermal Systems (POETS). This research used resources of the Advanced Photon Source at Argonne National Laboratory.

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Presenters

  • Jungwoo Shin

    • Materials Science and Engineering, University of Illinois at Urbana-Champaign

Authors

  • Jungwoo Shin

    • Materials Science and Engineering, University of Illinois at Urbana-Champaign

  • Jaeuk Sung

    • Materials Science and Engineering, University of Illinois at Urbana-Champaign

  • Minjee Kang

    • Materials Science and Engineering, University of Illinois at Urbana-Champaign

  • Byeongdu Lee

    • X-ray Science Division, Argonne Natl Lab
    • Advanced Photon Source, Argonne National Laboratory
    • Argonne National Laboratory
    • X-ray Science Division, Argonne National Laboratory

  • Cecilia Leal

    • Materials Science and Engineering, U. of Illinois, Urbana-Champaign
    • Univ of Illinois - Urbana
    • University of Illinois at Urbana-Champaign
    • Materials Science and Engineering, University of Illinois at Urbana-Champaign

  • Nancy Sottos

    • Materials Science and Engineering, University of Illinois at Urbana-Champaign

  • Paul Braun

    • Materials Science and Engineering, University of Illinois at Urbana-Champaign

  • David Cahill

    • Materials Science and Engineering, University of Illinois at Urbana-Champaign
    • Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign
    • University of Illinois at Urbana-Campaign
    • University of Illinois at Urbana-Champaign
    • University of Illinois at Urbana–Champaign
    • Department of Materials Science and Engineering and Materials Research Laboratory, Univ of Illinois - Urbana
    • Univ of Illinois - Urbana
    • Univ of Illinois at Urbana-Champaign
    • Department of Materials Science and Engineering, University of Illinois