Anionic Polymerization of Butadiene Using Lithium/Potassium Multi-metallic Systems: Influence on Polymerization Control and Polybutadiene Microstructure

Thermal, mechanical, and viscoelastic properties of polybutadiene-based rubber materials are highly dependent on polybutadiene microstructure. The use of polar modifier in association with alkyllithium is a well-known method to obtain polybutadiene with a high vinyl content. Another approach is to use bimetallic initiating species such as alkyllithium combined to heavier alkali metal alkoxide (RONa, ROK…). The polymerization control is nevertheless not achieved and several parameters were found to influence it. Using bimetallic initiating systems based on alkyllithium and a potassium alkoxide, alkyllithium structure, initiator preformation time, and initiator composition were identified as parameters influencing the anionic polymerization process of butadiene and/or polybutadiene microstructure. In addition, the use of trimetallic systems based on alkyllithium, potassium alkoxide, and alkylaluminum was investigated in order to prevent side reactions regardless of the [K]/[Li] ratio and of the initiator preformation time.