Styrene metal surface sites

Further support for the proposed mechanism is provided by the results of experiments involving phenylbromide instead of ethylbromide (Jj6). The polarizable TT electrons of this aryl compound allow it to effectively compete with styrene for the sites on the lithium surface and thus the Wurtz coupling reaction becomes dominant. Similar results were obtained with ethyltosylate. Although the reaction of tosylate with living polystyrene is rapid and quantitative, yielding ethyl capped polymers, its reaction with the monomer and metallic lithium produces only 10% of the ethyl capped polymers, the remainder being evolved as butane. Again, the aromatic nature of tosylate allows it to compete with styrene for the lithium sites. 

The early studies demonstrated the possibility of initiating polymerization by intensive mechanical dispersion of certain inoiganic substances, including metals (Fe, Al, Mg, Cr, W) in vinyhc monomers. The degree of polymerization of styrene, vinyl acetate, acrylonitrile, or MMA depended on the dispersion intensity. The fresh metal surfaces play the role of catalyst and initiator. These surfaces are the sites of electron transfer from the surfaces metal atoms to the monomers to form ion-radical initiating particles. Colloidal particles of Au, Tl, and Pt were found to influence substantially the bulk and solution polymerization of styrene. - ... 

This observation has been used by Kargin, and Plate (127) who initiated polymerization and grafting with the help of mechanically disrupted inorganic materials. Many metals, oxides, and salts which never normally act as initiators, when mechanically disrupted, are able to initiate polymerization of styrene, methyl methacrylate, acrylonitrile, and other vinyl monomers. The surface of the active inorganic substance can also be used as a site for grafting to already existing polymer chains if joint dispersion of polymer and monomer, such as cellulose and styrene, is performed. 

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