Ultraviolet and infrared two-wavelength modulated self-healing materials based on azobenzene-functionalized carbon nanotubes

Photo-induced self-healing materials, which can be controlled remotely, instantly and precisely, are attracting increasing attention in various fields. However, it still remains challenging to modulate the self-healing materials with integrated functionalities possessing multiple-wavelength photo-responsiveness. Herein, we report a strategy of building a photo-responsive self-healing system capable of performing ultraviolet (UV) and near-infrared (NIR) two-wavelength induced double-repair. The strategy is based on azobenzene-functionalized multiwalled carbon nanotubes (MWCNTs) via a two-step method. Oxidized MWCNTs were first reacted subsequently with thionyl chloride, glycol, and 2-bromoisobutyryl bromide to yield MWCNT-Br macroinitiators. Then atom transfer radical polymerization (ATRP) of azobenzene monomer, 6-(4-butyl-4'-oxyazobenzene) hexyl methacrylate (Azo), was directly initiated by MWCNT-Br, affording MWCNT-PAzo nanocomposites. The MWCNT-PAzo system can undergo photothermal- and photochemical-induced solid-liquid phase transition to manipulate the self-healing behavior while MWCNTs act as photo-absorbers/heat sources and azobenzene moieties serve on glass transition temperatures (T-g) switchers, in response to NIR and UV light stimuli, respectively. To our best of knowledge, this is the first-time that MWCNT-PAzo nanocomposites possess two-wavelength photo-responsiveness and exhibit excellent self-healing performance through the irradiation of two-wavelength bands (365 and 808 nm) of UV/NIR light.