Macromolecules 1994,27, 5957-5963
5957
Efficiency of the see-Butyllithiumlm-Diisopropenylbenzene Diadduct as an Anionic Polymerization Initiator in Apolar Solvents Y.S. Yu, R. J6r8me,' R. Fayt, and Ph. Teyssi6 Center for Education and Research on Macromolecules (CERM), University of Likge, Sart Tilman B6, 4000 Likge, Belgium Received May 6, 1994; Revised Manuscript Received July 25, 1994'
ABSTRACT: The 2/1 sec-butyllithium/l,3-diisopropenylbenzene adduct has been prepared and evaluated as an effective, hydrocarbon soluble, difunctional initiator for the synthesis of polystyrene-polybutadienepolystryene (SBS) thermoplastic elastomers in cyclohexane or benzene solution. The molecular weight distribution of both the PBD central block and the final block copolymer is narrow, and the expected molecular weight is obtained. However, mechanical testing, degradation of the PBD component,and use of an excess of s-BuLi compared to DIB suggest that the final copolymersare diblock instead of triblock as expected. The stoichiometricreaction of s-BuLi with DIB in an apolar solvent essentially results in the expected Li diadduct. This organolithium compound does not however react as a difunctional anionic initiator in a hydrocarbon solvent, but rather as a monofunctional compound more likely due to an association process. Addition of enough THF can make approximately two species active per DIB molecule. The addition of small amounts of triethylamine (
