Fusion of core-shell capsules serving as model nanoreactors

在自然界中，许多化学反应是在空间有限的环境中进行的。例如，在细胞内，这种反应可以在时间和空间上耦合。在一个反应室中进行的某一反应的产物往往是后续过程的反应物或催化剂。在多室系统中，不相容反应也可以同时发生。迄今为止，人工核/壳微胶囊和纳米胶囊主要是通过两亲性嵌段共聚物作为聚合囊泡（聚合体）的自组装，或通过在牺牲的固体颗粒上逐层沉积聚电解质来制备的。在fusion - caps中，详细研究了一种利用具有梳状接枝结构的两亲性聚电解质在油滴周围组装成胶囊的方法，该方法通过融合具有相反电荷的胶囊来实现纳米容器。fusion - caps的主要目标是：(1)了解在水中分散的充油核壳聚合物纳米胶囊的形成机制和性质；(2)揭示带相反电荷的纳米胶囊融合形成纳米反应器的机制和影响因素；(3)利用胶囊融合产生的密闭疏水环境进行选定的化学反应。本文提出的通过填充油的纳米胶囊的融合来实现纳米反应器的新途径将为融合聚合物组装体的形成动力学提供重要的基础见解，并可能提供前所未有的控制分散在水介质中的稳定疏水反应环境的途径，这可能具有绿色合成化学的优势。在fusion - caps中，我们解决了胶囊的制造问题，这些胶囊装载试剂，并在聚变后作为纳米反应器使用，其特性可以系统地针对所需的反应进行定制。对于选定的熔合胶囊，模型过程，包括能量传递和碰撞淬火，以及化学反应，如“点击”和Diels-Adler反应，将通过荧光光谱和时间分辨荧光显微镜等方法进行详细研究。最后，将揭示纳米反应器的尺寸和性质对这些反应的限制的影响。

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.