Préparation de Macromolécules à Structure en Etoile, par Copolymerisation Anionique

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<jats:title>Abstract</jats:title><jats:p>Star‐shaped macromolecules have been obtained by anionic block copolymerization of a monofunctional monomer and a divinyl compound with cumylpotassium or butyllithium as initiator. The polymer molecule is a crosslinked nodulus, to which n linear, solvated chains are attached. The shielding effect of these chains is such that more than 40% difunctional monomer is necessary to induce gel formation in the reaction medium. Star‐shaped polystyrenes, polyisoprenes, polyvinylpyridines and poly(methyl methacrylate) were obtained by this method, the crosslinking agent being divinylbenzene or glycol dimethacrylate. The individual branches of the star molecules may be considered identical, but a polydispersity arises from the fact that within a sample the number of branches of the star molecules fluctuates appreciably. Fractionation remains possible, though it is not very easy to get monodispersed samples. The molecular dimensions of the star‐shaped polymers, as determined from their intrinsic viscosities or from their radii of gyration, are smaller than those of the corresponding linear polymers, and this may be considered a proof of their highly branched structure.</jats:p>

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