Doubly-Threaded Polycatenanes and Polyrotaxanes

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With this award, the Macromolecular, Supramolecular, and Nanochemistry Program in the Division of Chemistry is funding Dr. Stuart J. Rowan from University of Chicago to develop synthetic methods to build new polymer architectures and to study how these architectures impact polymer properties. Conventionally, polymers or long chain molecules are prepared from smaller molecules that are joined together by carbon-carbon covalent bonds. Covalent bonding occurs when pairs of electrons are shared by atoms and it constitutes the basic building principle for all of organic chemistry. The approach in this work is rather unique because the repeating units in the targeted polymers are not covalently bonded to one another, yet cannot be separated unless covalent bond breakage occurs. Essentially, the monomer units are interlocked together like individual pieces in a metal chain or necklace. The molecular version of two interlocked rings is called a catenane and, when they are liked together the overall structure is a polycatenane (it looks like a metal chain). A related interlocked polymer in which a long polymer molecule is threaded through a ring molecule, like beads on a string, is called a polyrotaxane. Such interlocked polymeric materials may have unique physical properties and potential applications in the areas of molecular electronics, energy absorbing materials, nanorecording and optical bioimaging. The activities associated with this award increase broadening participation and enable training of high school, undergraduate, and graduate students in synthetic organic chemistry and polymer chemistry. The outreach program 'Natures Materials' is created as a part of the Cleveland Museum of Natural History's Martin Luther King Discover Day which demonstrates how natural polymers are used everyday. Both polycatenanes and polyrotaxanes consist of components that are interlocked together and held in place with a mechanical bond. In this research, an investigation on how the structure of the components can be used to impact product distribution, molecular weight, and the resulting properties of polycatenanes is conducted. In addition, research activities expand the types of interlocked polymers that can be accessed via the metallosupramolecular template approach to doubly-threaded poly[3]rotaxanes and slide ring gels. The access to such new interlocked polymeric structures, along with a better structure/property understanding of such systems, allows the development of materials with the potential to exhibit an unusual property matrix. These structures open the door to new polymeric actuators and materials.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.