Hierarchical Assembly of Two-Dimensional Polymers into Colloidosomes and Microcapsules

Hierarchical assembly of two-dimensional (2D) polymers to 3D microstructures provides new means of creating functional materials with exotic properties for extensive applications. Herein, we report an approach of assembling 2D covalent organic framework (COF) colloidosomes or microcapsules from small molecules. We polymerized monomers to produce narrowly distributed COF particles with average particle sizes greater than 490 nm, which were further used as stabilizers to prepare various water-in-oil Pickering emulsions with droplet sizes of 10-120 mu m on average. The emulsion droplets were subsequently applied as templates for interfacial polymerization of the same monomers. The COF microcapsules with varied diameters and shell thicknesses of 0.2-3.1 mu m were thus obtained, which possessed good stability, high crystallinity, and surface areas no less than 540 m(2)/g. The approach also permits facile loading of water-soluble substances such as salts, dyes, or proteins. The loaded molecules demonstrated different permeability against the shell, in which 98% of the encapsulated salts could be released in 1 h while only 18% of dye molecules and almost none of the fluorescent proteins diffused out from the microcapsules. Such an assembling approach may greatly extend the applications of 2D polymers and their microcapsules.

Automated summary

Hierarchical assembly of 2D polymers into 3D microstructures offers new opportunities for creating functional materials with unique properties. In this study, COF microcapsules were assembled from small molecules and used as templates for interfacial polymerization, resulting in microcapsules with good stability, high crystallinity, and the ability to load water-soluble substances. This approach has the potential to expand the applications of 2D polymers and their microcapsules.