Non-cross-linked hollow polymer nanocapsules of controlled size and shell thickness

In this work, we report the synthesis of non-cross-linked, spherical, hollow polymer nanocapsules of low dis-persity in aqueous media. For this, well-defined diblock copolymer brushes, comprising a poly(methyl meth-acrylate) (PMMA) inner block and a poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) outer block, were grown from the surface of silica spheres via surface-initiated atom transfer radical polymerization (SI-ATRP). Robust, hollow polymer nanocapsules were obtained in water following the etching of the inorganic core, with the hydrophobic PMMA block ensuring the structural integrity of the hollow colloids, while the hydrophilic PDMAEMA outer layer allowed their dispersion in aqueous media. The stability of the hollow polymer nano -capsules was found to require a minimum molecular weight and a high glass transition temperature of the solvent incompatible inner block, while the rigidity of the polymer shell was influenced by the length of the PMMA block as well as the grafting density of the polymer chains on the silica surface. The protocol for the synthesis of hollow polymer nanocapsules established in this work, overcomes the main challenges encountered to date in the preparation of polymer nanocapsules, related to low synthetic yields, polydispersity in size and the requirement to permanently cross-link the polymer chains to retain the capsule stability in the solvent medium. The nanocapsules reported in this study can be prepared at high yields, with tunable sizes and low dispersity in the absence of chemical cross-links.

Automated summary

This work presents a method for synthesizing non-cross-linked, spherical, hollow polymer nanocapsules of low dispersity in aqueous media. The nanocapsules were obtained by growing well-defined diblock copolymer brushes from the surface of silica spheres via surface-initiated atom transfer radical polymerization (SI-ATRP). The hollow polymer nanocapsules demonstrated high yields, tunable sizes, and low dispersity without the need for chemical cross-links.