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.

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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