The main objective of this proposal is to fully comprehend how ATRP (Atom Transfer Radical Polymerization) proceeds in systems with very small amounts of transition metal catalyst, and also to determine how to design an optimal catalytic/redox system to diminish the amount of catalyst while retaining sufficient polymerization control. We propose to explore structure-reactivity effects of various metals, ligands, and reducing agents, as well as the effect of medium and temperature on new ATRP systems that proceed with ppm amounts of copper catalyst. The main intellectual challenge is to precisely determine kinetic and thermodynamic parameters for all elementary reactions involved and to correlate the structure of the key reagents with their reactivity. We will measure equilibrium constants, stability constants, redox potentials and halide affinities for the most active ATRP catalysts. We will also study the behavior of complexes with new multidentate ligands and with charged ligands. We will measure the extent of a plausible disproportionation and quantify interactions of reducing agents with catalysts. We will also determine rate constants of all relevant reactions. The obtained data will be used to construct a comprehensive model that can be applied under various conditions, for a large range of monomers, and for better architectural control. This will also help to expand range of polymerizable monomers and diminish concentration of transition metal catalysts. The generated knowledge will help advance organic atom transfer reactions and will also provide leads to industry for more benign ATRP processes. We anticipate that the research from this proposal will have a broad impact by educating graduate and undergraduate students as well as postdoctoral fellows. Information will be disseminated in the form of timely publications, on the internet, and through presentations at (inter)national symposia and the outreach program at Carnegie Mellon University. We continue the Controlled Radical Polymerization Consortium with ~ 15 companies that will benefit from the knowledge generated by the NSF supported activities. We expect that the proposed research to be supported by the NSF will impact not only synthetic polymer chemistry but also materials science and may lead to the development of some commercially valuable materials.
