Visible-light-switchable glass transition temperatures and optical actuation in crosslinked fluoroazopolymers

Nature has provided significant inspiration for designing polymer materials that can move in response to light, with many examples of such materials created, especially using ultraviolet (UV) light as an external stimulus. However, it is essential to design materials that can regulate the mechanical properties of polymers through visible light stimulation and macroscale movement under visible light exposure. Here, we have developed a polymer film chemically crosslinked with fluorinated azobenzenes, which produces a strong mechanical response when exposed to green or blue light in air. The film exhibits visible-light-switchable mechanical properties and directional bending due to the photoisomerization of azo chromophores in the crosslinked polymer networks. The thin film also changes their optical transparency upon visible light irradiation. This work offers insights into the development of responsive polymer materials and photomechanical materials, advancing the realization of self-propelled machines and soft robotics powered by visible light.