Role of chain transfer reactions in the formation of molecular weight distribution of polybutadiene prepared by means of an organosodium initiator containing tetrahydrofuran

Abstract

It has been shown by studying the molecular mass distribution of polybutadiene in either toluene or heptane solutions with a tetrahydrofuran-containing organosodium initiator that in the presence of an organoaluminium modifier the molecular mass distribution of polymers prepared in either solvent is governed by the chain transfer to monomer; the relative rate constant of the chain transfer reaction is of the order of 10 −3. In the absence of the modifier, chain transfer to toluene plays an important role as well. The temperature dependence of the rate constant of the chain transfer reaction was measured for polymerizations carried out in heptane. The character of the resulting distribution was compared with the assumed structures of the active centres, coexisting in the polymerizing system.