With this award, the Organic and Macromolecular Chemistry Program supports the work of Professor Thomas S. Hughes of the University of Vermont. This research involves carrying out novel synthetic approaches to carbon single-walled nanotube segments with specific and controllable structural parameters such as the length, diameter and chiral vector, or the orientation of the six-membered rings of carbon atoms relative to the axis of the tube. These approaches to the strained nanotube segments rely on the synthesis of planar, unstrained phenylene macrocycles containing alkyne or cyclopentadienone functional groups. These planar macrocycles will be synthesized and then additional phenyl groups will be added using a Diels-Alder cycloaddition. The phenyl groups are introduced in an arrangement that will allow a subsequent oxidation reaction to fuse the rings together into the target tubular structures. Control over the diameter and length of the product nanotubes will be achieved by controlling the diameter of the precursor macrocycle and the size of the auxiliary phenyl-containing reactants. The strain inherent in the nanotube segments will thus be incorporated in a highly incremental fashion. Once synthesized, the solid-state packing and the conductivity of the nanotube segments will be evaluated. Chemical modifications of the segments will also be performed analogous to those currently carried out on larger nanotubes with less well-defined structures; such chemical modifications of these model systems will elucidate the chemical events taking place in the larger nanotubes.
The broader impacts of this project are in part the training of graduate students in organic synthesis and characterization, and in the characterization of organic materials. In addition, the product nanotube segments are models of the larger carbon single-walled nanotubes currently produced with relatively little control over their diameters and lengths. The segments produced by the method proposed may be suitable as "seeds" for the production of large amounts of nanotubes with specific structures. Since the structure of the carbon nanotube affects its potential usefulness as a material for organic electronic applications such as field-effect transistors, light-emitting diodes and photovoltaics, these smaller model systems could be used to further the understanding of the physical bases of these phenomena and could be potential feedstocks for materials in eventual devices.
