Divinylidene compounds and their role as key compounds for the synthesis of blockcopolymers

Abstract

Divinylidene compounds with isolated double bonds of the type are quantitatively transformed into soluble dilithio organic compounds with sBuLi and may be used as bifunctional initiators for the anionic polymerization of butadiene (B) and subsequently styrene ( S ) . Beside the expected SBS block copolymers also SB block copolymers are obtained because of partial termination of the dilithio compounds.By means of GPC analysis of the reaction compounds, i. e., of the homopolybutadiene, the blockcopolymers and the homopolystyrene after oxidative degradation using dual detection it is proved that the bifunctional species because of intramolecular association adds the monomer with significantly lower rate than the monofunctially growing species. Choosing suitable conditions the rate differences may be minimized. ZUSAMMENFASSUNG:Divinylidenverbindungen mit isolierten Doppelbindungen vom Typ 0 1984 Huthig & Wepf Verlag, Base1 OOO3-3146/84/$03.00 53 T. Bastelberger and H. HBcker lassen sich mit sBuLi quantitativ in losliche dilithioorganische Verbindungen iiberfuhren und als bifunktionelle Initiatoren fur die anionische Polymerisation von Butadien (B) und anschlienend Styrol (S) verwenden. Neben den erwarteten SBS-Blockcopolymeren finden sich infolge partiellen Abbruchs der Dilithiumverbindung auch SB-Blockcopolymere. Durch gelchromatographische Analyse der Reaktionsprodukte auf der Stufe der Homopolymeren und der Blockcopolymeren unter Verwendung eines Dualdetektors lie13 sich feststellen, dal3 die bifunktionelle Spezies infolge intramolekularer Assoziation eine wesentlich geringere Wachstumsgeschwindigkeit aufweist als die monofunktionelle Spezies. Durch Wahl geeigneter Bedingungen lassen sich die Unterschiede minimieren.

Dilithium initiators based on 1,3‐bis(1‐ phenylethenyl)benzene. Tetrahydrofuran and lithium sec‐butoxide effects

“…16 The stoichiometric reaction of m-diisopropenylbenzene with two moles of sec-butyllithium has been reported to produce a useful, hydrocarbon-soluble dilithium initiator because of the low ceiling temperature of the m o n~m e r~~~~~ which is analogous in structure to a-methylstyrene; however, other studies suggest that oligomerization occurs with this divinyl compound also and that functionalities higher than two result.27 Higher functionalities have also been reported for the analogous precursor, 1,lbis(4-isopropenylphenyl)-l-phenyltride~ane.~~ A plethora of divinyl aromatic compounds have been evaluated as precursors for hydrocarbonsoluble dilithium initiators' without the emergence of a simple, stable, reproducible initiating system until recent work with 1,3-bis( 1-phenyletheny1)benzene. [29][30][31][32][33][34] The addition reaction of sec-butyllithium with 1,3-bis( 1-phenyletheny1)benzene (eqns (l), (2)) proceeds rapidly and efficiently to produce the corresponding dilithium species with a rate constant for the second addition (k,, eqn (2)) which is equal to the rate constant for the first addition (kl, eqn (1)) in toluene solution,35 but an order of magnitude larger in cy~lohexane.~' It has been reported that this dilithium initiator is not only soluble in hydrocarbon media such as cyclohexane, benzene and toluene (even at -20"C32), but also functions as an efficient difunctional initiator for the preparation of CH, CH, I 1 II 1 2 3 homopolymers and triblock copolymers with relatively narrow molecular weight distribution^.^' -3 1…”

Synthesis and Evaluation of Multifunctional Anionic Initiators Based on n‐BuLi and Meta‐Diisopropenyl Benzene

“…The use of aromatic and aliphatic solvents often leads to formation of inactive aggregated species. Many authors studied syntheses of lithium‐based initiators in different solvents and observed that solvent effects can be remarkable, possibly because of the modification of the polarity of the reacting medium. For instance, Yu et al showed that the reaction between sec‐BuLi and DIB is slower in cyclohexane than in benzene.…”

Synthetic and mechanistic aspects of anionic polymerization

“…In both cases, however, intramolecular association of living ends disturbs the polymerization [8,9]. butyl lithium to form a bifunctional lithium initiator which is soluble in toluene and may be used as initiator for t h e anionic polymerization of butadiene.…”