Anionic polymerization of butadiene by dialkylmagnesium / alkali metal alkoxide systems in apolar medium: Polybutadiene microstructure and polymerization control

Abstract

Lithium based anionic polymerization of butadiene in apolar media allows the obtention of polybutadiene with a high vinyl content by using polar modifier or alkali metal alkoxide. For instance, butadiene polymerization with alkyllithium and potassium tert-pentoxide produces polybutadiene with 50% of vinyl content. The aim of this paper is to develop an approach without any alkyllithium moieties in order to synthesize polybutadiene with a high vinyl content (50%–70%) in a controlled way. To do so bi-metallic systems based on di-n-butylmagnesium in association with potassium or sodium tert-pentoxide were studied in apolar medium. The influence of parameters such as the initiator preformation time and the [Mt]/[Mg] ratio were assessed (Mt = K, Na). The potassium tert-pentoxide-based system was found to produce polybutadienes in a controlled way with 50% of vinyl content, while polybutadienes with up to 70% of vinyl content were obtained in a controlled way with Na based systems.