Classification of polar additives with respect to their influence on the microstructure in anionic polymerization of butadiene with butyllithium by transition energy measurements

On the basis of so-called linear free enthalpy correlations, a method is de veloped to predict vinyl contents of polybutadienes from anionic polymeriza tions with butyllithium in nonpolar solvents in the presence of bases. Acco rding to Reichardt with an extension by Langhals, a transition energy scale for the solvatochromic dye N,N-dimethyl indoaniline in dependence of conce ntrations of some bases is established. The bases were taken from polymeriz ations of butadiene of Antkowiak et al. and of Jin et al. It could be shown that vinyl contents determined by these authors correlate well with measur ed transition energies over the whole concentration range of the bases. Als o, temperature dependences of vinyl contents can be predicted satisfactoril y. Furthermore, it was found that vinyl contents in polybutadienes depend f or weak bases primarily on the polarity of the solution mixture determined by the base concentration and not on the molar ratio of base to initiator. The results are extensively discussed in comparison with earlier attempts i n the literature to predict the microstructure in polybutadienes in depende nce of polar modifiers. (C) 1999 John Wiley & Sons, Inc.