Flexible Chlorinated Azine Molecular Crystals and Their Photothermally Driven Actuation

This study explores the photochemical actuation of three crystalline azine derivatives, a class of organic compounds distinguished by the presence of the –C═N–N═C– functional group. Acicular crystals of the three symmetrically substituted o-, m-, and p-chloro derivatives of azine displayed remarkable elastic deformation when subjected to stress. The presence of the photoswitchable functional group –N═C– in the azine derivatives prompted us to investigate the UV light-induced mechanical effects on the single crystals and composite polymer membranes of the compounds. It was observed that the fast and reversible motion displayed by the single crystals is due to the photothermal effect exhibited by the compounds, which was also reflected in the irreversible curling motion of the composite polymer films.