[Nature Chemistry] Photoswitching of Glass Transition Temperatures of Azobenzene-containing Polymers Induces Reversible Solid-to-liquid Ttransitions
writer：H.W.Zhou,C.G.Xue, P.Weis,Y.Suzuki, S.L.Huang, K.Koynov, G.K.Auernhammer, R.Berger, H.J.Butt,S.Wu,*
keywords：Azobenzene-containing Polymers,
source：期刊
specific source：Nature Chemistry, 2017, 9, 145-151.
Issue time：2017年
The development of polymers with switchable glass transition temperatures (Tg) can address scientific challenges such as the healing of cracks in high-Tg polymers and the processing of hard polymers at room temperature without using plasticizing solvents. Here, we demonstrate that light can switch the Tg of 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 Tg above room temperature, whereas cis azopolymers are liquids with Tg below 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 Tg provides a new strategy for designing healable polymers with high Tg and allows for control over the mechanical properties of polymers with high spatiotemporal resolution.