Cyclodextrin‐Based Hollow Nanocapsules Synthesized Using Catalytic Templates

Cyclodextrin‐based hollow nanocapsules were synthesized by a core‐shell method using catalytic silica nanoparticle cores and a β‐cyclodextrin‐based polyurethane shell. Silica nanoparticles prepared by the “Stober” method were first functionalized with a molecular spherical monolayer of the tertiary amine‐terminated silane, N , N ‐dimethyl‐3‐aminopropyltrimethoxysilane, a catalyst for the polyurethane reaction between cyclodextrin and a diisocyanate. Exposure of the catalytic nanoparticle templates to a solution containing β–cyclodextrin and tolylene‐2,4‐diisocyanate resulted in self‐terminating polymerization around the templates. The reason that polymerization self‐terminated was that the surface catalytic tertiary amine monolayer on glass spheres became buried as the polyurethane coating formed and thereby inactivated in their catalytic activity. Curing of the core‐shell composite materials followed by removal of the silica core templates with hydrofluoric acid yielded robust, hollow polymeric nanocapsules with spherical voids.