Macromonomers living polymerization

Polymerizations of methacrylic monomers in the presence of methacrylic macromonomers under monomer-starved conditions display many of the characteristics of living polymerization (Scheme 9.36). These systems involve RAFT (Section 9.5.2). However, RAFT with appropriate thiocarbonylthio compounds is the most well known process of this class (Section 9.5.3). It is also the most versatile having been shown to be compatible with most monomer types and a very wide range of reaction conditions.382... 

Chain transfer to methacrylate and similar maeromonomers has been discussed in Section 6.2.3.4. The first papers on the use of this process to achieve some of the characteristics of living polymerization appeared in 1995.380 The structure of macromonomer RAFT agents (163) is shown in Figure 9.3. An idealized reaction scheme for the case of a MMA terminated macromonomer is shown in Scheme 9.36. 

Conventional radical polymerization usually produces polymers with a broad distribution in DP. The polymers are mixtures of the instantaneous polymers with DPw/DPn of at least 1.5 for the termination by recombination or 2.0 either for the termination by disproportionation or for the chain transfer to small molecules. In this respect, any living polymerization with rapid initiation will afford polymers with a narrow DP distribution of the Poisson type. Ring-opening met-hathesis polymerization of norbornenyl-terminated macromonomers, 8, 15, and 16, appears promising in this regard [22,23]. 

Radical homopolymerization and copolymerization of macromonomers are fairly well understood and reveal their characteristic behaviors that have to be compared with those of conventional monomers. A detailed mechanism of the polymer-polymer reactions involved, however, appears still to be an issue. Ionic or, desirably, living polymerization and copolymerization are still an important... 

Techniques derived from anionic or cationic living polymerization methods have widely been used. They are efficient because of the long lifetime of the active sites. Once polymerization is completed these sites are used for functionalization purposes. Alternately, unsaturated ionic initiators have been used but to a lesser extent because of the requirement involved that the polymerizable groups remain unscathed during the macromonomer formation. The versatile inifer method has also been applied to the synthesis of macromonomers. 

Living polymerization processes pave the way to the macromolecular engineering, because the reactivity that persists at the chain ends allows (i) a variety of reactive groups to be attached at that position, thus (semi-)telechelic polymers to be synthesized, (ii) the polymerization of a second type of monomer to be resumed with formation of block copolymers, (iii) star-shaped (co)polymers to be prepared by addition of the living chains onto a multifunctional compound. A combination of these strategies with the use of multifunctional initiators andtor macromonomers can increase further the range of polymer architectures and properties. 

DPE-functionalized macromonomers were also used for linking reactions with living polymeric anions,... 

Living polymerizations provide the most versatile synthetic routes for the preparation of a wide variety of well-defined polymer structures. Macromonomers... 

Living polymerization created the idea of Macromer (proposed by R. Milkovich, generic term is macromonomer) for synthesizing a graft copolymer of well-controlled structure. We reported the synthesis of polydimethylsiloxane (PDMS)... 

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