Photo-controlled properties and functions of azobenzene-terminated polymers

Azobenzene is a photoswitchable compound, which shows trans -to- cis isomerization under UV irradiation and cis -to- trans isomerization under visible light irradiation. Compared with azobenzene small molecules, azobenzene-containing polymers (azopolymers) showed improved mechanical properties and good processibility, which make them promising candidates for photoresponsive materials. In the past, azopolymers with different architectures, such as homopolymers, random copolymers, block copolymers, hyperbranched polymers, terminated polymers and others, have been studied. The architecture of azopolymers plays an important role for their photoresponsive properties, functions and applications. In this Feature Article, we focus on azobenzene-terminated polymers. The design, synthesis, properties and potential applications of azobenzene-terminated polymers are introduced. In particular, their photoresponsive properties in solutions, gels and bulk materials are discussed. The potential applications of azobenzene-terminated polymers based on photoinduced hydrophobic-to-hydrophilic changes and solid-to-liquid transitions are highlighted. Finally, some remaining challenges in the field of azobenzene-terminated polymers are discussed.