Controlled/living radical transition metal catalyzed

Tsuyoshi Ando received his bachelor degree in 1995, master degree in 1997, and Ph.D. degree in 2000 from Kyoto University. His doctoral study was on the development of transition-metal-catalyzed living radical polymerization systems under the direction of Professor Mitsuo Sawamoto, where he received a Research Fellowship for Young Scientists of the Japan Society for the Promotion of Scientists (1998-2000). He joined the Kyoto University faculty, Department of Polymer Chemistry, Faculty of Engineering, as a research instructor in 2000. His research activity is focused on controlled reactions, including precision polymerization, catalyzed by metal compounds. 

Now that many facile controlled/living radical polymerization systems have been developed for a wide range of monomers, many researchers have adopted them as a tool for preparing well-defined stmcture polymers not only in polymer chemistry ° but also in the biochemical, medical, and optoelectronic fields. Among the various radical polymerization systems, the transition metal-catalyzed atom transfer process is one of the most promising processes in terms of controllability, facility, and versatility. In this reaction, one polymer chain forms per molecule of organic halide as an initiator, while a catalytic amount of the metal complex serves as an activator, which would homolytically cleave the carbon-halogen terminus (Scheme 1). 

Transition Metal Complexes tor Metal-Catalyzed Atom Transfer Controlled/Living Radical Polymerization 431... 

WangJ-S, Matyjaszewski K Living /controlled radical polymerization. Transition metal-catalyzed atom transfer radical polymerization in the presence of a conventional radical initiator. Macromolecules 28 7572-7573, 1995. 

In this reaction, one polymer chain forms per molecule of the organic halide (initiator), while the metal complex serves as a catalyst or as an activator, which catalytically activates, or homolytically cleaves, the carbon—halogen terminal. Therefore, the initiating systems for the metal-catalyzed living radical polymerization consist of an initiator and a metal catalyst. The effective metal complexes include various late transition metals such as ruthenium, copper, iron, nickel, etc., while the initiators are haloesters, (haloalkyl)benzenes, sulfonyl halides, etc. (see below). They can control the polymerizations of various monomers including methacrylates, acrylates, styrenes, etc., most of which are radically polymerizable conjugated monomers. More detailed discussion will be found in the following sections of this paper for the scope and criteria of these components (initiators, metal catalysts, monomers, etc.). 

This paper has provided, we believe, a comprehensive, up-to-date, critical, and objective review on the discovery and the subsequent fast development of living radical polymerizations catalyzed by transition-metal complexes in the period from 1994 to early 2001. These metal-catalyzed living radical polymerizations have rapidly been developing since their discovery in 1994, and the scope of applicable monomers, metal catalysts, and initiators has been expanding. Their advantages include versatility toward a variety of monomers, feasibility in a wide range of reaction conditions, and relatively easy access to the materials. This permits many researchers to use the systems for the precision synthesis of various polymers with controlled architectures. 

---