Synthetic Phosphorus Chemistry: The Systematic Development of Phosphorus-Containing Molecules and Polymers

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This goal of this research proposal is to systematically develop the chemistry of phosphorus and its compounds. Phosphorus is an important element, not only being essential for life but being used in a wealth of commercial products. The primary objective of our work is to develop polymers that contain phosphorus as a key component of the main chain. Most polymers in use today are comprised of chains containing carbon, oxygen, and/or nitrogen atoms in well-defined sequences. The incorporation of phosphorus into a polymer provides a additional chemical functionality due to its wide range of oxidation states, coordination numbers and bonding environments. Thus, phosphorus-containing macromolecules possess unique physical properties and chemical functionality that are not possible with solely organic polymers. For instance, phosphorus can reversibly bind to metals, thereby potentially providing access to a polymeric on-off switch. Despite the exciting prospects for phosphorus-containing polymers, they are still extremely rare. The key challenge to the widespread usage of P-containing polymers is the lack of general synthetic routes to incorporate inorganic elements into long chains. The addition polymerization of the C=C bond of olefins is perhaps the most important method of industrial polymer production being used to make polyethylene, polypropylene polystyrene, acrylics, and Teflon, to name a few. It was long believed that heteroatom-containing multiple bonds were not suited for addition polymerization methods. We were the first to extend addition polymerization to P=C bonds. In doing so, we discovered that P=C bonds are fascinating building blocks for a variety of new molecules and materials. The development of P=C molecules and polymers comprises a key topic of this proposal, including in new areas such as self-healing materials. We will also develop an entirely new area of heteroatom analogues of poly(isoprene) and related dienes. Polyisoprene is natural rubber, a hugely important commercial going back to the discovery of Goodyear. By polymerizing phosphorus-versions of natural rubber, we are opening up huge possibilities of functional versions of natural rubber (including flame retardancy). In a final area of pursuit, we are developing p-conjugated polymers with unique photophysical properties. The presence of phosphorus in these materials can function as a chemical switch whereby the luminescence of the polymer may be turned on and off through the binding to certain metal analytes. Thus, these materials are attractive as sensors. In closing, the work proposed herein further expands the fascinating chemistry of phosphorus. This work will lead to gains in fundamental knowledge of inorganic chemistry and polymer science, and will provide a foundation for future technological applications.