Addition of Unsaturated Monomers to Rubber and Similar Polymers

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Abstract
The addition of different ethylene monomers to polyisoprene was studied in order to throw a light on reaction mechanisms and structures of reagents. It was attempted, during the planned transformations, to maintain as best as possible the shapes and sizes of initial macromolecules, upon which rests the property of high elasticity. For this purpose, it was decided to avoid grafting reactions, as well as any reactions affecting the nature of the polyisoprenic chain, e.g., scission, cross-linking, and cyclization. After the completion of the work carried out by one of the authors on the addition of maleic anhydride, the existence of two mechanisms was brought to light: the one is of a radical type, produced by adding an unsaturated reagent on a methylene close to a double bond of chain; the other is of a thermal nature, triggered by the action not of a catalyst, but of a rather high temperature. It is clear that the latter process does involve isomerization of a part of chain double bonds. The model to which maleic anhydride is connected has been deduced by examining the reaction aptitudes of a series of monomers. The major part of highly polymerizable materials, with the exception of acrylonitrile, were eliminated a priori, in order to avoid both homopolymerization reactions and graftings. The monomers in which double bonds are depleted in π electrons are more apt to give the desired reactions. The more favorable effect is obtained with α carbonyl (maleic anhydride and γ crotonolactone). Other factors were also taken into account. The work reviewed here enabled us to assess the way in which reactions evolve according to the considered mechanisms and produce new macromolecular materials. The resulting compounds have a high rubberlike elasticity and show a high chemical reactivity, due to anhydride or lactone side groups.

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