Premium
Diene polymerization by mixed sodium‐ and lithiumalkyl initiators in hydrocarbon medium
Author(s) -
Pakuro Natalia I.,
Zolotareva Irina V.,
Kitayner Alla G.,
Rogozhkina Elena D.,
Izyumnikov Anatoliy L.,
ArestYakubovich Alexander A.
Publication year - 1995
Publication title -
macromolecular chemistry and physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.57
H-Index - 112
eISSN - 1521-3935
pISSN - 1022-1352
DOI - 10.1002/macp.1995.021960127
Subject(s) - isoprene , chemistry , polymer chemistry , polymerization , polymer , sodium , hydrocarbon , lithium (medication) , toluene , anionic addition polymerization , diene , organic chemistry , copolymer , medicine , natural rubber , endocrinology
Polymerization of butadiene and isoprene initiated by the hydrocarbon‐soluble mixture 2‐ethylhexyllithium/2‐ethylhexylsodium in toluene was studied. The components of the initiator when taken separately give rise to polymers greatly different in both their molecular weight and microstructure: living polydienes with high 1,4‐unit content are formed when alkyllithium is used while organosodium initiators produce polymers of high 1,2(3,4)‐structure and of low molecular weight due to strong chain transfer to toluene. Polymers obtained with mixed initiators were found to have the same structure as the “sodium” ones, while their molecular weights are either the same as those of the polymers obtained with alkyllithium alone (in the case of butadiene) or decrease gradually with increase of sodium content in the initiator (in the case of isoprene). The calculations performed show that the simple scheme assuming chain propagation through individual lithium and sodium active centres and fast exchange of counter‐ions between them cannot explain the results obtained. It is suggested that the true active centres in mixed systems are bimetallic complexes containing both sodium and lithium atoms simultaneously.