Fusion of core-shell capsules serving as model nanoreactors

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In Nature, many chemical reactions take place in spatially confined environments. For instance within cells, such reactions can be coupled in time and space. Products of a given reaction executed in one reaction chamber are often the reactants or catalysts of a subsequent process. In multicompartment systems also incompatible reactions can be realized simultaneously. Artificial core/shell micro- and nanocapsules have thus far been mainly fabricated by self-assembly of amphiphilic block copolymers as polymeric vesicles (polymersomes), or by exploiting layer-by-layer deposition of polyelectrolytes on sacrificial solid particles. In FUSION-CAPS a new approach to realize nanocontainers via fusion of capsules of opposite charge is investigated in detail, which is based on capsules formed by the assembly of amphiphilic polyelectrolytes with comb-like graft architecture around oil droplets. The objectives of FUSION-CAPS are in particular (1) to understand the mechanism of formation and the properties of oil-filled core-shell polymer nanocapsules dispersed in water, (2) to unveil the mechanism of fusion of nanocapsules with opposite charges to form nanoreactors and the factors that govern it, and (3) to exploit the confined hydrophobic environments generated by capsule fusion for performing selected chemical reactions. The new route to nanoreactors proposed here via fusion of oil-filled nanocapsules will offer important fundamental insight into the formation dynamics of fused polymeric assemblies and may afford access to unprecedented control of stable hydrophobic reaction environments dispersed in aqueous media, which may possess advantages for green synthetic chemistry. In FUSION-CAPS we address the fabrication of capsules that are loaded with reagents and serve after fusion as nanoreactors, whose properties can be systematically tailored for the desired reactions. For selected fusing capsules, model processes, including energy transfer and collisional quenching, as well as chemical reactions, such as "click" and Diels-Adler reactions, will be studied in detail by fluorescence spectroscopy and time resolved fluorescence microscopy methods, among others. Finally, the impact of the confinement due to the dimensions and properties of the nanoreactors on these reactions will be unveiled.