Design and characterization of functionalized silica nanocontainers for self-healing materials

Silica nanocapsules functionalized with thiol or amine groups with sizes between 100 and 400 nm could be successfully synthesized using the interface of direct miniemulsion droplets for the hydrolysis and condensation of silicon alkoxides. We show that healing agents such as monomers and catalysts can be successfully encapsulated in the silica shell. The catalyst was encapsulated as a solution to allow a better mobility when released for a self-healing reaction. The functional groups were quantified by Si-29 MAS-NMR, XPS, and chemical titration. Therefore a precise picture for the gradient of concentration of functional groups inside the shell could be given. The encapsulated reagents were found to be still active and the self-healing reaction could be successfully monitored by solid-state NMR spectroscopy and thermogravimetry.