Study of copolymerization of butadiene with styrene by the action of bis-triphenylmethyl barium in tetrahydrofuran

From Limestone to Catalysis: Application of Calcium Compounds as Homogeneous Catalysts

“…Anionic polymerization of activated alkenes, such as styrene, butadiene, or isoprene, is classically initiated by catalytic amounts of alkyllithium reagents. However, it was already found at an early stage that addition of group 2 alkoxides influences the microstructure of the polymer . A mixed organolithium/calcium alkoxide initiator gave in the polymerization of styrene and butadiene a highly random copolymer with mainly trans -linkages (arising from trans -selective 1,4-butadiene insertion) .…”

Anionic polymerization of butadiene by dialkylmagnesium / alkali metal alkoxide systems in apolar medium: Polybutadiene microstructure and polymerization control

“…In terms of butadiene polymerization control, little informations were found and one can assume side reactions similar to the one reported for organosodium-initiated polymerization. The use of alkylcalcium ([8]- [15]), strontium [15] and barium ([15]- [17]) derivatives are reported to produce polybutadiene with a low vinyl content (10 -25%) and a 1,4-cis / 1,4-trans ratio ranging from 0.16 to 7 in apolar media. Such alkaline earth based initiators are not readily available and metal activation is often required through the use of amalgam or electronic transfer in THF [18].…”