Multifunctional Polymer Networks Crosslinked via Covalent Organic Cages

拟议的研究项目涉及新的交联聚合物的开发，轴承单独定义的化学环境。这些化学环境将进一步使得能够引入不同的功能。为了实现这一点，正在测试一种全新的交联类型。代替仅用化学反应性基团装备聚合物链，特殊的几何结构被并入作为聚合物链的端基。这些分子端基可以根据动态共价化学的原理反应以形成不同的分子笼结构。因此，所得聚合物网络将具有笼状结构作为键。约翰逊教授及其同事的研究小组已经成功地测试了基于金属-有机笼状化合物（金属=钯）的催化活性聚合物材料的制备。 我选择的方法允许构建全有机材料，并将两种不同的笼引入同一材料。这种类型的交联允许定制材料特性，例如与通常实现的相比，在更宽的范围内的粘弹性。其原因是大量的聚合物链在一个交联节点处连接在一起。通过巧妙地选择聚合物链末端的分子结构，必须能够在同一聚合物网络中构建至少两种不同的笼状结构。 如果这是成功的，非弹性网络缺陷的数量可以大大减少，这将使材料性能更接近理论极限。在最后一步中，笼式连接件内不同但限定的化学环境将配备有额外的功能。因此，应该可以将功能集成到聚合物网络中，如果没有笼内的定位，这些功能将不相容。

The proposed research project deals with the development of new crosslinked polymers, bearing separated defined chemical environments. These chemical environments will further enable the introduction of different functionality. To make this possible, a completely new type of crosslinking is being tested. Instead of equipping polymer chains exclusively with chemically reactive groups, special geometric structures are incorporated as end groups of the polymer chains. These molecular end groups can react according to the principles of dynamic covalent chemistry to form diverse molecular cage structures. Thus the resulting polymer networks will have cage structures as linkages. The preparation of catalytically active polymer materials based on metal-organic cage compounds (metal=palladium) has already been successfully tested by the research group of Prof. Johnson and co-workers. The approach I have chosen allows the construction of all-organic materials and the introduction of two different cages into the same material. This type of cross-linking allows to tailor material properties such as viscoelasticity over a broader spectrum compared to what is usually achieved. The reason for this is the high number of polymer chains that are linked together at one cross-linking node. By clever choice of the molecular structures used at the ends of the polymer chains, it must be possible to build at least two different cage structures within the same polymer network. If this is successful, the number of non-elastic network defects can be drastically reduced, which would enable material properties much closer to the theoretical limit. In a final step, the different but defined chemical environments inside the cage linkages will be equipped with additional functionality. Thereby, it should be possible to integrate functionalities into the polymer networks that would not be compatible without the localization inside the cages.