Visible‐Light‐Triggered Actuators Based on the Molecular Crystals of Anthracenecarbonitrile Undergoing Reversible [4+4] Cycloaddition

Abstract The photomechanical effects of crystals of halogen‐substituted 9‐anthracenecarbonitrile were investigated. The needle‐like crystals of 10‐fluoroanthracene‐9‐carbonitrile ( FCNA ) bend rapidly under irradiation with 365 nm, 410 nm light and even white light, and the bent crystal could almost recover to its original shape upon exposure to 254 nm light or heating. The reversible photo‐induced mechanical behaviors originated from [4+4] cycloaddition and the reverse reaction. This type of photoactuator, in response to light irradiation over a broad wavelength range from UV to the visible region, might have important applications in biomimetic systems, biomedicine, artificial muscles, and smart microrobotics. The rapid photo‐induced mechanical movements of the crystals inspired us to fabricate a hybrid polymer film of polyvinylidene difluoride incorporated with the microcrystals of FCNA , which not only showed bending toward or away from the light source depending on the initial bending direction of the film, but also could lift small objects induced by remote light.