Polymer–silica hybrid self-healing nano/microcapsules with enhanced thermal and mechanical stability

In recent years, microencapsulation technology has drawn much attention due to its wide applications. Added to the coating as a dry powder, the microcapsules contain a liquid that can repair the film if released into the cracks. However, there is still a lack of synthesis strategies for microcapsules with excellent strength, solvent resistance and thermal stability. Herein, organic–inorganic hybrid nano/microcapsules loaded with isophorone diisocyanate (IPDI) were prepared via interfacial polymerization in Pickering emulsion. The diameter of the resultant capsules ranged from 468 nm to 1106 nm, and the thick shells were densely packed with silica nanoparticles. To evaluate the resistance properties of the nano/microcapsules, thermogravimetric analysis (TGA) tests showed that the capsules have a high initial evaporation temperature at about 340 °C; titration tests indicated that the capsules exhibited outstanding resistance to xylene and acetone. For capsules characterized by AFM, the compressive modulus could reach up to 16–19 GPa, which proved their excellent mechanical property. The morphology of the nanocapsules in different preparation periods was also studied, and it was found that the shell wall was closely packed with silica nanoparticles. The structure of the shell wall and the chemical reaction between organic and inorganic materials improved the hardness of the nano/microcapsules. Furthermore, the resultant capsules exhibited self-healing ability in an organic silicon resin coating.