Anisotropic Azopolymer Nanotube Arrays via Photo-Fluidization for Applications in Directional Water Transportation

In recent years, polymer nanoarrays have become popular research topics in materials science because of their unique properties. However, achieving precise control over the directional orientations of polymer nanoarrays remains a challenge that is critical for applications such as directional water transportation. In this work, we present a versatile approach to preparing anisotropic polymer nanotube arrays by utilizing the photofluidization behavior of azobenzene-containing polymer (PAzo). Solid-state step polymerization and the postazo-coupling reaction are applied to synthesize PAzo. Subsequently, PAzo is introduced into the nanopores of anodic aluminum oxide templates using the solvent vapor annealing method. Upon selective etching of the templates, PAzo nanotube arrays are released. Irradiation with linearly polarized light induces trans-cis-trans photoisomerization in the azobenzene groups of PAzo, resulting in elongation of the nanotubes along the direction of polarization. The resulting anisotropic PAzo nanotube arrays exhibit distinct water contact angles in parallel and perpendicular directions. This strategy offers a promising avenue for the fabrication of anisotropic polymer nanotube arrays with potential applications in directional water transportation.