Synthesis coordination polymerization

Mason, A.F., and Coates, G.W. (2007) Coordination polymerization synthesis of new homo- and copolymer architectures from ethylene and propylene using homogeneous Ziegler-Natta polymerization catalysts. Macromolecular Engineering, 1,217-249. 

Moreover, the molecular catalysts have provided systematic opportunities to study the mechanisms of the initiation, propagation, and termination steps of coordination polymerization and the mechanisms of stereospecific polymerization. This has significantly contributed to advances in the rational design of catalysts for the controlled (co)polymerization of olefinic monomers. Altogether, the development of high performance molecular catalysts has made a dramatic impact on polymer synthesis and catalysis chemistry. There is thus great interest in the development of new molecular catalysts for olefin polymerization with a view to achieving unique catalysis and distinctive polymer synthesis. 

Radical polymerization is the most useful method for a large-scale preparation of various kinds of vinyl polymers. More than 70 % of vinyl polymers (i. e. more than 50 % of all plastics) are produced by the radical polymerization process industrially, because this method has a large number of advantages arising from the characteristics of intermediate free-radicals for vinyl polymer synthesis beyond ionic and coordination polymerizations, e.g., high polymerization and copolymerization reactivities of many varieties of vinyl monomers, especially of the monomers with polar and unprotected functional groups, a simple procedure for polymerizations, excellent reproducibility of the polymerization reaction due to tolerance to impurities, facile prediction of the polymerization reactions from the accumulated data of the elementary reaction mechanisms and of the monomer structure-reactivity relationships, utilization of water as a reaction medium, and so on. 

The first example of Iiving polyolefin with a uniform chain length was found in the low-temperature polymerization of propylene with the soluble catalyst composed of V(acac)3 and Al(C1Hi)2Cl. The mechanism of the living coordination polymerization is discussed on the basis of the kinetic and stereochemical data. Subsequently, some applications of living polypropylene are introduced to prepare tailor-made polymers such as terminally functionalized polymers and block copolymers which exhibit new characteristic properties. Finally, new types of soluble Ziegler-Natta catalysts are briefly surveyed in connection with the synthesis of living polyolefins. 

The first example of a living polyolefin with a uniform chain length was disclosed in 1979 by Doi, Ueki and Keii 47,48) who used the soluble Ziegler-Natta catalyst composed of V(acac)3 (acac = acetylacetonate anion) and A1(C2H5)2C1 for the polymerization of propylene. In this review, we deal with the kinetics and mechanism of living coordination polymerization of a-olefins with soluble Ziegler-Natta catalysts and the synthesis of well-defined block copolymers by the use of living polyolefins. 

As mentioned in section 4.1, the kinetics of the living polypropylene synthesis have been interpreted in terms of a coordination polymerization mechanism represented by Eq. (22). We discuss here the mechanism of chain propagation on the basis of the structure and stereochemistry of the synthesized polypropylenes. 

This chapter surveys the synthesis of functional polymers by direct methods, such as anionic, cationic, bee radical and coordination polymerization, as weU as post-polymerization functionalization of chains in the bulk or on the surface. Special emphasis is given to more modem techniques that allow for controlled and directed functionalization via living polymerization. Moreover, an introduction to typical applications of functional polymers is presented. 

Coordination polymerization involves the use of transition metal catalysts. Examples are Ziegler-Natta polymerization by Tl/Al systems, metallocene polymerization with Ti, Zr, Hf catalysts, or metathesis polymerization with W, Mo, Re metals. Synthesis of functional polymers by organometallic catalysts are particularly difficult because transition metds are not only l ed by protic functionality, they are often poisoned by heteroatoms (e.g. N, O). 

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