Entangled Polymers by Design Using Supramolecular Chemistry

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In this project funded by the Macromolecular, Supramolecular and Nanochemistry Program of the Chemistry Division, Harry Gibson of the Virginia Polytechnic Institute and State University will synthesize and study macromolecules in which branch points, crosslinks or repeat units are mechanical connections in the form of rotaxanes or catenanes. A variety of polymerization techniques (e. g., anionic, atom transfer radical, nitroxide mediated, classical free radical and ring opening metathesis) will be employed to prepare well-defined macromolecules with terminal, central or multiple host and guest functionalities. These polymers will then be self-assembled into a variety of topologies (star, H-branched, poly[2]rotaxane, bottle brush, etc.) in both homopolymeric and copolymeric forms, all involving rotaxane linkages, some topologies not readily accessible otherwise. These supramolecular rotaxane polymers are expected to exhibit enhanced properties relative to covalent polymers because of the restoring force between the cyclic and linear components present in the rotaxane units. Morphological, rheological, thermal and mechanical studies will elucidate the novel properties and responses of these systems that distinguish them from normal covalently linked macromolecules, providing new insights into the ultimate properties that are achievable through supramolecular science. The broader impacts involve training undergraduate and graduate students as well as postdoctoral researchers, an ongoing commitment to training students from groups underrepresented in the chemical sciences, and disseminating research results through publications in journals and presentations at conferences.This work will enhance our fundamental understanding about polymers linked mechanically via interlocking loops and chains and their physical behavior. Polymer chains are the fundamental units of many plastic materials, and the development of new types of polymers could lead to new applications in biomedical materials, coatings, and composites.