Reversible and Non-reversible Mechanically Connected Polymers and Copolymers

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With this award, the Macromolecular, Supramolecular and Nanochemistry Program of the Division of Chemistry is supporting Professor Harry W. Gibson at Virginia Polytechnic Institute and State University perform research on new polymeric materials. The research explores the use of mechanical linkages (threaded loops and knots) at the molecular scale to bind polymers together in novel ways. Polymers such as plastics are ubiquitous in everyday life and this research program seeks ways to efficiently prepare new and novel types of polymers with unusual and/or improved properties, e.g., self-healing, response to external stimuli, such as mechanical stress, heat, pH or solvents, and rubber-like elasticity. The interdisciplinary nature of this project provides valuable technical training to a diverse group of graduate and undergraduate students including those from underrepresented groups. Educational outreach to high schools is planned to include hands-on polymer-related activities and discussions of polymeric materials in everyday life. Increased inclusion of these topics in the graduate and undergraduate curriculum is expected to contribute to the preparedness of such students for technical careers in industry. The intersection of polymer chemistry and supramolecular science offers a fertile space for the design and preparation of new materials with unusual properties and potentially novel practical applications. High fidelity self-assembly processes for pseudorotaxanes and rotaxanes are planned and, if successful, should lead to the formation of polymeric architectures that involve mechanical linkages. Utilization of the threading principle with polymers that contain host species in the backbone would enable formation of unique bottle brush polymers whose structures can be varied widely and easily, providing entirely new types of polymers. These new materials with unusual architectures are expected to possess novel properties and the potential for new polymer applications. For example, the pseudorotaxane and rotaxane linkages in "slip-link" polymers are expected to display "self-healing" properties and a new type of elastomeric behavior, respectively. Morphological, rheological, thermal and mechanical studies are planned to elucidate the novel properties and responses of these systems that distinguish them from covalent macromolecules, providing new insights into the properties that may be achievable through supramolecular science.