Mechanistic Studies of Atom Transfer Radical Addition and Polymerization

Carnegie Mellon University, Pittsburgh PA

Investigators

Abstract

Professor Krzystof Matyjaszewski of the Department of Chemistry at Carnegie Mellon University is supported by the Organic and Macromolecular Chemistry Program for research on atom transfer radical polymerization, which is based on the use of radical polymerization to convert monomer to polymer. The purpose of the proposed research is to determine the structure of the catalytic and intermediate species in both ATRA and ATRP, and to build structure-reactivity correlations for alkyl, halide, metal and ligand components of the reactions. These objectives will be met by employing an array of chemical analysis techniques as well as examination of the kinetics and products of the model compound reactions. More specifically, the structures of the catalyst in non-polar media will be determined for various metal/ligand complexes using EXAFS, EPR, UV-Visible and other spectroscopic methods. This is required because very little information regarding the structures of such complexes in non-polar media (such as vinyl monomers) exists. Another area of focus is the determination of activation and deactivation rate constants of alkyl halide/metal catalyst pairs. The ability of ATRA and ATRP to produce well-controlled products depends heavily on these kinetic parameters, and therefore their determination is of vital importance in the development of new and more efficient catalysts. The systematic investigation of the structures and reactivities of the species involved in ATRA and ATRP will lead to a greater depth of understanding of these reactions. This will, in turn, advance and optimize both synthetic methods, such as the development of more effective catalysts, so that new materials (including small organic compounds and polymers) can be produced more efficiently and with greater yields and selectivity. Professor Krzystof Matyjaszewski of the Department of Chemistry at Carnegie Mellon University using atom transfer radical polymerization (ATRP) has been able to polymerize a wide range of monomers including various styrenes, acrylates and methacrylates as well as other monomers such as acrylonitrile, vinyl pyridine, and dienes. Although many of the polymer types described have been prepared using other living polymerizations, ATRP remains the most powerful, versatile, simple, and inexpensive. Researchers have been striving to develop a living radical polymerization for nearly 40 years. An alternative was sought because other types of living polymerizations are severely limited by many factors: only a small number of monomers can be used, the reactions are sensitive to moisture, and two or more monomers cannot be randomly copolymerized. Radical polymerization, in contrast, can polymerize hundreds of monomers, can copolymerize two or more monomers, and can be performed in water as emulsions or suspensions. The Matyjaszewski research group was the first to develop a "controlled/living radical polymerization" (CRP) that used a simple, inexpensive polymerization system. It is capable of polymerizing a wide variety of monomers, is tolerant of trace impurities (water, oxygen, and inhibitor), and is readily applicable to industrial processes. The system that was developed was termed Atom Transfer Radical Polymerization (ATRP). ATRP is a robust system that has generated much interest among polymer chemists in both industry and academia. Science Watch, a trade journal, has recently listed three ATRP papers among the top ten cited papers in chemistry today. Several commercial companies are pursuing CRP as evidenced by 195 patent applications with 72 related to ATRP alone. The first commercial product related to this method will be available this year. The first applications are related to coatings but applications related to dispersants, adhesives, additives, lubricants, and cosmetics will quickly follow.