Polymerization of Butadiene Initiated by Lithium Alkylamide- Hexamethylphosphoric Triamide System

Abstract

Polymerization of butadiene initiated by lithium alkylamide (LiNR₂) was studied. The polymerization does not occur with LiNR, in hydrocarbon media, but the reactivity of LiNR₂ increases markedly in the presence of hexamethylphosphoric triamide (HMPA), which initiates the 1, 2-polymerization of butadiene.
By adding three moles of HMPA to one mole of LiNR₂, the exothermic polymerization occurs and 88-89% of polybutadiene has 1, 2-structure without cis-1, 4-structure.
It was found that the microstructure is independent of the amount of HMPA and a type of amides added. An approximate linear relationship exists between the logarithm of the amount of catalyst and that of the polymer viscosity. After polymerization of butadiene, when styrene is added to the polymerized mixture, butadiene styrene block copolymer is formed. From these results, this polymerization would proceed by means of the mechanism of living type.