Numerous microencapsulation techniques have been developed to encase various chemicals, for which specific processing parameters are required to address the widely differing features of the encapsulated materials. Microencapsulation of reactive agents is a powerful technique that has been extensively applied to self‐healing materials. However, the poor solvent compatibility and insufficient thermal stability of microcapsules continue to pose challenges for long‐term storage, processing, and service in practical applications. Here, an easily modifiable and highly versatile method is reported for preparing various chemicals filled poly(urea‐formaldehyde) microcapsules that exhibit superior tightness against solvents and heat and that possess widely tunable, repetitiously self‐restorable, and solvent‐proof superhydrophobicity. In addition, the low‐cost fabrication of biomimetic multifunctional smart coatings is demonstrated for self‐healing anticorrosion and self‐cleaning antifouling applications by directly dispersing the superhydrophobic microcapsules into and onto a polymer matrix. The methodology presented in this study should inspire the development of multifunctional intelligent materials for applications in related fields.

HDI-filled silica/polyurea hybrid microcapsules with superior thermal stability and solvent resistance were prepared and applied to one-part self-healing anticorrosion coatings.

Double-layered polyurea microcapsules containing hexamethylene diisocyanate (HDI) with outstanding shell tightness have been successfully synthesized via interfacial polymerization reaction in an oil-inwater emulsion. The resultant capsules were systematically characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. The reaction parameters including reaction temperature (40 C, 50 C, 60 C), reaction duration (1 h, 1.5 h, 2 h and 2.5 h), amount of Suprasec 2644 (2.4 g, 3 g and 3.6 g) and emulsification time (15 min, 45 min and 75 min) were investigated and evaluated in terms of core fraction and quality of microcapsules. The core fraction of microcapsules was reduced with an increase of reaction temperature, reaction duration, mass of Suprasec 2644 and emulsification time, while the quality of microcapsules fluctuated. The thermal and organic solvent resistances were assessed by using TGA and titration. The results showed that the microcapsules had 1.6% weight loss compared with pure HDI with 90% weight loss after 60 min isothermal treatment at 100 C. After immersion in various solvents for 24 days, the microcapsules released as low as $3% of core in weakly polar solvents (i.e. hexane and xylene), about 5-60% in polar aprotic solvents (i.e. ethyl acetate, acetone, DMF and DMSO), and 60-90% in water and polar protic solvents (i.e. isopropanol and ethylene glycol). Both fresh and hexane-treated HDI capsules showed excellent anticorrosion performance in scratched coatings via self-healing functionality, indicating promising practical application in industrial coating and paint systems.