title: Photoswitching of glass transition temperatures of azobenzene-containing polymers induces reversible solid-to-liquid transitions.
abstract: The development of polymers with switchable glass transition temperatures (Tg) can address scientific challenges such as the healing of cracks in high-Tgpolymers and the processing of hard polymers at room temperature without using plasticizing solvents. Here, we demonstrate that light can switch the Tgof azobenzene-containing polymers (azopolymers) and induce reversible solid-to-liquid transitions of the polymers. The azobenzene groups in the polymers exhibit reversible cis-trans photoisomerization abilities. Trans azopolymers are solids with Tgabove room temperature, whereas cis azopolymers are liquids with Tgbelow room temperature. Because of the photoinduced solid-to-liquid transitions of these polymers, light can reduce the surface roughness of azopolymer films by almost 600%, repeatedly heal cracks in azopolymers, and control the adhesion of azopolymers for transfer printing. The photoswitching of Tgprovides a new strategy for designing healable polymers with high Tgand allows for control over the mechanical properties of polymers with high spatiotemporal resolution.
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Hongwei
authors.initials: H
authors.lastname: Zhou
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Changguo
authors.initials: C
authors.lastname: Xue
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Philipp
authors.initials: P
authors.lastname: Weis
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Yasuhito
authors.initials: Y
authors.lastname: Suzuki
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Shilin
authors.initials: S
authors.lastname: Huang
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Kaloian
authors.initials: K
authors.lastname: Koynov
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Günter K
authors.initials: GK
authors.lastname: Auernhammer
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Rüdiger
authors.initials: R
authors.lastname: Berger
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Hans-Jürgen
authors.initials: HJ
authors.lastname: Butt
authors.affiliation: Max Planck Institute for Polymer Research, Ackermannweg 10, 55128 Mainz, Germany.
authors.forename: Si
authors.initials: S
authors.lastname: Wu