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5699045 
Journal Article 
Classification of polar additives with respect to their influence on the microstructure in anionic polymerization of isoprene with butyllithium by transition energy measurements 
Beckelmann, D; Bandermann, F 
1999 
Yes 
Journal of Applied Polymer Science
ISSN: 0021-8995
EISSN: 1097-4628 
John Wiley and Sons Inc. 
73 
8 
1533-1547 
English 
WOS:000081006900022 
A transition energy scale was established on the basis of dimethyl indoaniline as organic dye for 23 mono-and bidentate polar additives. From polymerization experiments of isoprene with s-butyllithium in mixtures of n-hexane and the selected bases, the microstructure of polyisoprenes was determined by 1H-NMR spectroscopy. The vinyl contents of these polymers could be satisfactorily correlated with the transition energy measurements. However, it turned out that especially bidentate bases do not fit into this scheme. Obviously, besides their influence on the polarity of the reaction solution, they exhibit special interactions with the growing centers. The developed correlations allow the prediction of 1,2-and 3,4-linkages in polyisoprenes from anionic polymerization of isoprene with butyllithium in polar solvents in the presence of low concentrations, also of bases hitherto not investigated. The temperature dependence of the microstructure can likewise be estimated. As in the case of butadiene, at least for weak bases, it was found that the vinyl contents depend primarily on the polarity of the reaction mixture determined by the base concentration and not on the molar ratio of base to initiator. © 1999 John Wiley & Sons, Inc. 
anionic polymerization; polar additives; isoprene; microstructure; transition energy measurements