Abstract
In previous kinetic investigations it was found that polymerization initiated by alkyllithium in hydrocarbon media is not a typical anionic process. The peculiarities of this type of polymerization have been explained by the participation of both carbanion and lithium components of an active center in the chain propagation. In connection with suggestions previously made, the effect of the solvents (toluene, triethylamine, ethyl ether, dioxane, and tetrahydrofuran) on the homoβ and copolymerization of styrene, butadiene, and isoprene in the presence of ethyllithium was studied. It was found that in hydrocarbon media these monomers form mutually associated βlivingβ polymers. Regarding the nature of monomers the degree of association increases as follows: styrene < isoprene < butadiene. The reactivity of these monomers increases in the same sequence. The solvation of the growing lithium chains or its association complexes with monomers gives rise to the possibility of chain propagation in hydrocarbon media by a twoβstep mechanism. In electronβdonating solvents the total activation energy of polymerization decreases, and reaches a minimum in THF. The relative reactivity of the investigated monomers in chain propagation increases in the sequence: isoprene > butadiene > styrene.