Supramolecular Dynamics in Solution and in Gels

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Supramolecular chemistry occupies the space between individual molecules and macroscopic systems in terms of complexity and functionality. Two key features of supramolecular systems are: 1) the reversible assembly of a supermolecule from molecular building blocks and 2) the co-existence of related species that compete with one another. These characteristics are those exhibited in very complex macroscopic living systems. My research aims to understand the dynamic nature of supramolecular systems and will provide the concepts necessary for rational control of these systems from the kinetic point of view. Such kinetic control, which is currently lacking, will open new ways to design functional materials, where the dynamics of the components are essential for function. The research proposed is at the forefront of fundamental studies and does not directly address any particular function, but the outcomes have implications for any supramolecular system where binding and release of building blocks is integral to function, such as membrane transport, drug delivery, catalysis, or stimuli-responsive materials. The proposed research is allied with “systems chemistry”, in which interactions of molecular building blocks produce new properties that the individual components cannot achieve on their own.To develop and exploit inherently complicated systems, we need to develop tools to explore and manipulate the system's outcomes. The proposed work confronts the diversity of supramolecular systems, with a focus on the kinetic control of gel-forming systems.The proposed work with cucurbit[n]urils (CB[n]s) as host systems will provide the tools to manipulate the dynamics of host-guest systems. This knowledge will lay the groundwork for rationally using kinetics to change the behaviour of systems with multiple species, which currently is not possible. The mechanistic diversity we uncovered for guest binding with CB[n]s will be explored to determine how co-adjuvant players can lead to switches in mechanism, how self-sorting systems can be diverted as they evolve, and how the residence time of guests that simultaneously bind to CB[8] can affect the formation of gels.The mobility of small guests in gels will be studied over microscopic to macroscopic length scales to provide information focused on the gel's molecular components. This approach will uncover knowledge that is different from the macroscopic characterization usually reported for gels. This type of experiment, where the focus is on the kinetics of individual components and the relationship to the microscopic structural features of gels, is unprecedented. As a potential practical application, the proposed work will contribute to moving the development of gels away from a trial and error approach.