Halogenation reactions in polymers

This reaction may be the origin of at least some of the halogen found in polymers produced in alkyl halide solvents. 

The halogen groups in polymers can be readily converted to other functional moieties by various exchange reactions affording options of converting polymer 3 or 4 into multifunctional initiators or macromonomers. 

The addition of iodine to olefins is unique among these halogen reactions in its reversibility. As a result, the appropriate, more complex kinetic equation is required to allow for the equilibrium position of the reaction, or else a large excess of the olefin is used to drive the reaction substantially to completion. In solvents of low polarity (carbon disulphide, carbon tetrachloride) the reaction is of high order with respect to iodine. Groh et o/." believed to be an important polymer of iodine, since their investigations showed the term... 

Metal Oxides. Halogen-containing elastomers such as polychloroprene and chlorosulfonated polyethylene are cross-linked by their reaction with metal oxides, typically zinc oxide. The metal oxide reacts with halogen groups in the polymer to produce an active intermediate which then reacts further to produce carbon—carbon cross-links. Zinc chloride is liberated as a by-product and it serves as an autocatalyst for this reaction. Magnesium oxide is typically used with ZnCl to control the cure rate and minimize premature cross-linking (scorch). 

When unsaturatcd polymers have hydrogen or halogen atoms in a-position to the double bonds, they are especially sensitive to chain transfer by a free radical attack. Therefore in these cases, the graft copolymerization may involve a combination of two initiation processes which occur simultaneously and compete with each other, one by chain transfer, the other by addition copolymerization. The relative importance of both processes is again dependent on the nature of the polymerizing monomer and of the backbone polymer involved in the reaction. 

In view of the importance of preparing well characterized, halogen terminated polymers, there is an obvious need for a careful examination of the direct halogenation reaction. Optimization of the halogenation reaction, however, may not be straightforward, since it has been observed by ESR spectroscopy that radicals are formed in the reaction of simple alkyllithiums with bromine or iodine in the presence of equimolar amounts of Lewis bases such as N,N,N ,N -tetramethylethylenediamine or ether 328),... 

In order to limit extensive side reactions (advanced destruction of the support-polymer, modification of grafting monomers structure) which usually accompany grafting reactions in electrical discharge conditions, we have elaborated the solid-solid grafting procedure in cold plasma. Thus, the rayon fabric was grafted with halogen and phosphorus containing polymers in... 

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