Molecular design on dual stimuli-responsive azobenzene-containing ionic complexes toward self-healing materials under photoirradiation or humid condition at room temperature

Self-healing materials working at room temperature are attractive in the field of materials chemistry. Compared to those requiring one specific external stimulus, one smart material that can launch the self-healing process under multiple stimuli would accommodate more various working conditions. In this work, a double-chain azobenzene-containing surfactant AZO with good molecular flexibility and hydrophilicity is designed for developing self-healing materials with dual responses to light and humidity. By mixing AZO and surfactants containing linear aliphatic chains, the resulted composites gain crystal-to-isotropic liquid phase change ability under the trigger of either light or humidity, thanks to the formation of sufficient free volume for AZO molecules. This leads to the light-/humidity-induced self-healing materials at room temperature. Meanwhile, the composite of AZO and double-chain surfactant has been proved with better responsive sensitivity to light and humidity by forming a homogeneous molecular distribution. This study provides a new designing strategy for gaining dual self-healing materials working via an athermal way, promoting the development of smart materials with multiple stimuli-responsive property.