Polymérization anionique de l'isoprène par les insertions ternaires graphite–métal alcalin–solvant

Abstract

AbstractThe examination by HR–NMR of the microstructure of polyisoprenes synthesized in the presence of alkali metal–graphite compounds reveals that the polymerization has an anionic character. The microstructure of the polymers depends on the nature of the active centers, which depends on the solvent used in the preparation of the graphite compounds or as polymerization medium. With powdered alkali metal–graphite compounds, the propagation does not differ from the anionic one occurring in a homogeneous medium. Except for K–graphite, an enhancement of the 1–4 addition mode is observed if grains of Li or Na–graphite are used in mass polymerization. This change in the microstructure could be explained by the competition between the rate of propagation and the rate of diffusion of the growing chains from the grains to the homogeneous phase of the polymerization medium.