Polarization-induced alignment of azobenzene/fluorinated polyimide for three-dimensional shape-persistent and photo-responsive elastic helixes

Abstract Three-dimensional (3D) macroscopic chiral helixes using anisotropic polymer assembly shows a great potential for designing micromechanical systems and soft robotics. However, movement of flexible polymer chains make the fabrication of 3D macroscopic helical ribbons with excellent shape stability under high temperature or multitudes of stretch/strain cycling very problematic. This paper presents the polarization-induced alignment of a non-LC supramolecular azobenzene-polyimide assembly (Azo/f-PI). We prepare 3D left- or right-handed Azo/f-PI helixes with shape-persistence, high-elasticity and photoresponsivity by large-area molecularly oriented assembly films. The Azo/f-PI helix treated at 100 °C for 10 min retains its linear-elastic deformation with 77.16% retention of the elastic potential energy density (0.304 J/g), and an extremely low permanent deformation of 3.68% upon 1000 stretching-relaxation cycles. Moreover, the 3D helix exhibited a light-driven elongation up to about 175.0% of the original length under UV irradiation. This 3D high-elastic helix with excellent shape persistence and photo-responsive actuability opens a gate for micromechanical control.