Butyllithium Polymerization of Butadiene. III. Effect of Inactive Lithium Compounds

The effect of some lithium salts on the microstructures of low- DP polybutadienes was determined. Lithium alkoxides markedly increased extent of 1, 2 addition, and the increase was a function of the alkoxide/butyllithium ratio. Other salts, such as lithium hydride and lithium hydroxide, had little, if any, effect on polybutadiene micro-structure. The product from the reaction of 1-hexyne and butyl-lithium increased 1, 2 addition and also resulted in polybutadienyl lithium solutions that were very high in viscosity or gelled. The effect of lithium salts was taken as good evidence that the active species in monomer insertion is the organolithium complex which proceeds through the ionic species, LinR (n-1 ⊕R⊖. The viscosity effects obtained with hexynyl lithium were explained on the basis of the known facile formation of dilithio acetylides with the assumption that the propargylic lithium was an active initiator.