POLYMERIZATION OF STYRENE-BUTADIENE BLOCK-COPOLYMERS USING A DICARBANION INITIATOR MADE BY THE REACTION OF LITHIUM WITH ALPHA-METHYLSTYRENE

Linear styrene-butadiene block copolymers of the polyA-block-polyB-bloch-polyA type (SBS) have been synthesized using a dicarbanion initiator formed by the reaction of metal lithium and EL-methylstyrene. While being unable to initiate polymerization in cyclohexane and/or n-hexane, the diinitiator performed well in benzene. Various promoters such as tetrahydrofuran (THF), tetramethylethylenediamine, and hexamethylphosphoric triamide have been added during the making of diinitiators, resulting in initiators of different functionalities and activities. The presence of THF facilitated the formation of the diinitiator, and the resulting polymers made with this diinitiator have been analyzed and mechanically tested. The effect of process variables on the polymerization kinetics and molecular characteristics was also investigated.