Alkene polymerization overview

In the present overview, we tried to gather most of the industrial cationic polymerizations for alkenes, as well as for carbonyl and heterocyclic monomers. Our main objective was not to insist on the conventional processes which are already detailed in the specific reviews quoted all along the text, but to outline the up-to-date improvements, new products, and market trends every time the corresponding information had been made available. 

In this account, an overview of the methods employed for the synthesis of conjugated dienes and polyenes is presented. Dienes and polyenes with isolated double bonds are excluded, as they are accessed through methods usually employed for alkene synthesis. Oligomerizations and polymerization reactions leading to polyenes are also not covered. Synthesis of 1,2-dienes, i.e. allenes, is excluded from the purview as there is a volume in the present series devoted to this functional group. Synthesis of heterodienes, conjugated enol ethers, [n]-annulenes and related compounds are also not covered here. However, enynes, dienynes and enediynes syntheses have been included in a few cases in view of their emerging importance. 

The following sections will provide an overview of the living carhocationic polymerizations of the three most important monomer families, namely, isobutene, vinyl ethers, and styrenics. The reactivity of the monomers for carhocationic polymerization is directly related to the stabilization of the formed carbenium ion vinyl ethers are the most reactive monomers, followed by styrenics and. Anally, 1,1-disubstituted alkenes (Scheme 8.4). As a direct consequence of this stabilization, the reactivity of the formed carbocations is opposite to that of the monomer. 

In some cases where a reaction involving a radical species occurred within cobalt porphyrin complexes, it has been possible to trap transient cobalt porphyrin hydride species. This was indeed observed during the synthesis of organocobalt porphyrin that resulted from the reaction of cobalt(n) porphyrin and dialkylcyanomethylradicals with alkenes, alkynes, alkyl halides, and epoxide. A transient hydride porphyrin complex was also involved in the cobalt porphyrin-catalyzed chain transfer in the free-radical polymerization of methacrylate. The catalytic chain transfer in free-radical polymerizations using cobalt porphyrin systems has been extensively investigated and will not be treated in this section. Gridnev and Ittel have published a comprehensive overview of the catalytic chain transfer in free-radical polymerizations. ... 

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