Design and Synthesis of New Interlocked Polymers

University Of Chicago, Chicago IL

Investigators

Abstract

With the support of the Macromolecular, Supramolecular and Nanochemistry (MSN) program in the Division of Chemistry (CHE) and the Polymers program in the Division of Materials Research (DMR), Professor Stuart J. Rowan of the University of Chicago is developing synthetic methodologies for the preparation of poly[n]catenanes and poly[n]rotaxanes. Catenanes and rotaxanes consist of two or more components that are interlocked together and held in place by the mechanical bond. Catenanes are comprised of interlocked rings while rotaxanes consist of a ring that is interlocked with a dumbbell (a thread-like molecule with stoppers on either end large enough to prevent dethreading of the ring) component. Macromolecular or polymeric versions of these species are particularly intriguing as they offer new polymeric architectures in which the relative motions of the different components allow access to new and unique properties. While architectures such as poly[2]catenanes and main-chain poly[n]rotaxanes have been prepared, synthetic methodologies to poly[n]catenanes and doubly threaded slide ring gels have received much less attention. In such architectures, the mechanical bond is part of the polymer backbone and allows the macromolecules to expand/contract without significant activation energy. As a result, such polymers can exhibit unusual viscoelastic properties. This research will explore new synthetic protocols that will allow access to these intriguing macromolecules. The proposed research will mix different disciplines within the chemistry arena, from synthetic organic and metal coordination chemistry to polymer science and characterization. This integrated research approach will provide students at all levels with broad educational experiences covering these topics. Additionally, the integrated high school and undergraduate research and outreach activities will be designed to increase the fraction of underrepresented minorities in science and engineering. Specifically, the planned activities will involve high school students from Chicago’s south side. This research will focus on developing synthetic routes to new interlocked polymers based on catenanes and rotaxanes. A strong emphasis will be placed on synthetic methodologies that utilize metal-ligand coordination as the thermodynamic driving force to preorganize the organic components, followed by a covalent fixing either through ring-closing metathesis to access the poly[n]catenanes, or high-yielding, catalyst-free click chemistries to access the doubly-threaded slide ring gels. This project will also provide systematic investigation on how the structure of the building components can be used to impact product distribution, molecular weight, as well as the resulting properties of these unique polymers. Results associated with this work have the potential to advance polymer chemistry by addressing fundamental questions about mechanical linkages in polymeric systems. Moreover, doubly-threaded slide ring gels are expected to be of broad scientific interest as they serve both as models of networks with trapped entanglements as well as potential sources of materials with unusual mechanical and functional properties. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.