Multifunctional Polymer Networks Crosslinked via Covalent Organic Cages

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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.