Polymérisation anionique du méthacrylate de méthyle par les organo-alcalins-I : Polymérisation en milieu solvant aprotonique, étude des tacticités

Anionic polymerizations of methylmethacrylate, initiated by fluorenyl-alkali metals in ether media or in hexamethyl phosphotriamide, give syndiotactic polymers. Calculated differential entropies and enthalpies of activation between the iso- and syndiotactic placements reveal that in dioxane, tetrahydropyrane and tetrahydrofurane the syndiotacticity increases from K⁺ to Li⁺. With solvents having higher dielectric constant (such as hexamethyl phosphotriamide) or higher donating power (such as glyme 4), the tacticity of the polymers is not affected by the nature of the counter-ions.

It has been suggested that, with dioxane, tetrahydropyrane and tetrahydrofurane, the donating power is not strong enough to destroy the coordination bonds between the C=O groups of the living polymer chains and the counter-ions.