Ultrathin Polymer Nanotubes Assembled from Side-Chain Amphiphilic Alternating Azocopolymers for the Potential of Highly-Efficient and Photo-Controllable Dye Removal

Abstract

One-dimensional ultrathin organic nanotubes (UTONTs) are of favorable potential as absorbents due to their hollow nanostructures, high-aspect-ratio, large specific surface area, and tailorable functions. However, the development of polymer-based and stimuli-responsive UTONTs for highly efficient and controllable removal of pollutants remains challenging. Herein, we report the self-assembly of side-chain amphiphilic alternating azocopolymers to generate cationic and photoresponsive ultrathin polymer nanotubes (UTPNTs) with an average diameter of ∼548 nm and a tubular wall thickness of ∼2.8 nm. Owing to the photoisomerization of azobenzene units, a reversible transformation from the UTPNTs to ultrathin polymer vesicles (UTPVs, a vesicular thickness of 2.4 nm, a diameter of 115 nm) was achieved upon alterative irradiation with UV and visible light, proving the attractive photoresponsive feature. The proof-of-concept adsorption performance for both UTPNTs and UTPVs was evaluated toward the anionic dye Congo red, with a photocontrollable and highly efficient adsorption activity that was highly dependent on ultrathin hollow structures and electrostatic interactions. The as-prepared UTPNTs exhibited favorable adsorption capacity, with a large adsorption amount of 1248.3 mg·g^–1 and a short equilibrium time of ∼6 min, greater than that of UTPVs (638.2 mg·g^–1). Our work provides a simple strategy for generating stimuli-responsive UTONTs with desirable adsorption performance.