Vinyl monomers, controlled/living anionic polymerization

Controlled/Living Anionic Polymerization of Vinyl Monomers... 

PS macromonomers have been efficiently applied to the synthesis of well-defined polymer hybrids with controlled length of grafts. They are, in general, prepared via living anionic polymerization of styrene monomers and their treatment with vinyl compounds, such as -allyl, -undecenyl, and styryl compounds. 

The transformation reaction may be also possible by using an opposite strategy, from a controlled radical polymerization to a living anionic polymerization. The most widely applied controlled radical polymerization for this particular transformation is ATRP, due mainly to the fact that hydroxyl and amino groups, which are potential initiating sites for the AROP of certain monomers, are compatible with the ATRP of vinyl monomers. Examples of such transformations have been summarized recently [62, 63], while the general concept is shown in Scheme 11.15, based on an example of the combination ATRP of vinyl monomers with the AROP of lactides [71]. 

For carbon-based vinyl monomers, controlled polymerization has been traditionally achieved by ionic mechanisms [174]. The living anionic polymerizations of styrene and methyl methacrylate are quite common, resulting in preservation of the polymer functionality. However, alike the inorganic analogues the ionic polymerization mechanism is limited to a rather narrow class of monomers, under conditions of the most stringent purity. Therefore, the aim to develop a controlled free radical... 

Trapping experiments with malonate anions in the controlled/living polymerization of vinyl ethers initiated by mixtures of hydrogen iodide (HI) and Lewis acids revealed that the total concentration of the growing species (the sum of dormant and active) stays nearly constant and equal to that of the introduced initiator when monomer is present in the reaction mixture. However, after complete monomer consumption, the concentration of the growing species decays relatively rapidly [251,252]. 

Polar Vinyl Monomers The anionic polymerization of polar vinyl monomers is often complicated by side reactions of the monomer with both anionic initiators and growing carbanionic chain ends, as well as chain termination and chain transfer reactions. However, synthesis of polymers with well-defined structures can be effected under carefully controlled conditions. The anionic polymerizations of alkyl methacrylates and 2-vinylpyridine exhibit the characteristics of living polymerizations under carefully controlled reaction conditions and low polymerization temperatures to minimize or eliminate chain termination and transfer reactions [118, 119]. Proper choice of initiator for anionic polymerization of polar vinyl monomers is of critical importance to obtain polymers with predictable, well-defined structures. As an example of an initiator that is too reactive, the reaction of methyl methacrylate (MMA)... 

Alkyllithitim-initiated, anionic polymerization of vinyl monomers is a very useful synthetic method since the major variables affecting polymer properties can generally be controlled, e.g., molecular weight, molecular weight distribution, copolymer structure and composition, configurational microstructure, molecular architecture, and chain-end functionality. This control is a direct consequence of the fact that in the absence of reactive impurities many of these polymerizations are termination and chain transfer free therefore, the products of these polymerizations are living polymers" with carbanionic chain ends. 

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