An eco-friendly smart self-healing coating with NIR and pH dual-responsive superhydrophobic properties based on biomimetic stimuli-responsive mesoporous polydopamine microspheres

Abstract

Smart self-healing coatings containing stimuli-responsive materials have attracted tremendous interest recently due to their switchable and desirable functionalities with the changes of external environment. However, the fabrication of most smart self-healing coatings requires complex procedures and/or unfriendly chemicals, and the environmental durability of a coating is still considered as a major factor that influences its large-scale engineering applications. Herein, an eco-friendly smart self-healing coating with near infrared (NIR) and pH dual-responsive superhydrophobic and anti-biofouling properties was fabricated by simply mixing the biomimetic stimuli-responsive mesoporous polydopamine microspheres (polydimethylsiloxane-loaded mesoporous polydopamine microspheres, abbreviated as P-PDMS@MPDA MSPs) with waterborne resin and hydrophobic nanoparticles. The P-PDMS@MPDA MSPs were fabricated through an emulsion-induced interfacial anisotropic assembly strategy, followed by the abundant loading of hydrophobic PDMS. These biocompatible P-PDMS@MPDA MSPs with NIR and pH dual-responsive properties acted as the self-healing agents and green hydrophobic fillers. The P-PDMS@MPDA MSPs also provided source for outfield stimulated response and no additional responsive material was required for the self-healing process. Superhydrophobicity of the coating was achieved with these fluorine-free, non-toxic, and biocompatible materials. When damaged by the external environment, the coating could directly self-heal its superhydrophobicity and active anti-biofouling properties under the NIR or pH stimuli, owing to the release of low-surface-energy PDMS from the P-PDMS@MPDA MSPs. The cytotoxicity of the casting solution for this smart coating and the long-term self-healing superhydrophobicity of the coating in harsh environments, including exposure to UV irradiation and immersion in salt, strong acid, and strong base solutions, were investigated. This smart coating shows great promise for anti-fouling, anti-adhesion, and biomedical applications due to its excellent self-healing and biological properties. The MPDA-based stimuli-responsive microspheres can be extended to other functionalized smart coatings.