Poly,butadienes butyllithium

The synthesis and characterization of a series of dendrigraft polymers based on polybutadiene segments was reported by Hempenius et al. [15], The synthesis begins with a linear-poly(butadiene) (PB) core obtained by the sec-butyllithium-initiated anionic polymerization of 1,3-butadiene in n-hexane, to give a microstructure containing approximately 6% 1,2-units (Scheme 3). The pendant vinyl moities are converted into electrophilic grafting sites by hydrosilylation with... 

Standstrom [3] improved the elongation at break properties of tires by blending 70% di-poly(l,4-isoprene) with 30% poly(butadiene) containing a high trans content. The latter was prepared using barium di(ethylene glycol) ethyl ether, tri-octyl aluminum, and n-butyllithium as the reaction catalyst mixture. 

In this technique, used, e.g., for the synthesis of block copolymers of poly(styrene-h-butadiene-h-styrene) (SBS), a polystyrene block is formed by employing n-butyllithium as the initiator in an aromatic solvent. Butadiene monomer is then added to react with the polystyrene-lithium chain end to form the poly(butadiene) block. If the reaction was terminated at this stage, a poly(styrene-h-butadiene) copolymer would result, which has no thermoplastic properties. Therefore, styrene monomer is added to produce the triblock SBS. The process for the preparation of SBS is very carefully controlled to avoid the formation of a diblock, as the presence of any appreciable amount of SB dramatically reduces the thermoplastic properties of SBS. 

Block copolymers are obtained from aromatic diisocyanates and vinyl monomers, such as styrene, isoprene, and methyl methacrylate via anionic polymerization, using w-butyllithium as initiator (71). Since TDI imdergoes selective reaction through the nonhindered isocyanato group poly(butadiene-6Zoc -imide) block copolymers are obtained (72). 

The polymers are crystalline and have a linear head-to-tail 1,4 enchainment with a trans-di-isotactic structure the two lateral substituents of each base unit are in the erythro steric positions as revealed by IR and X-ray data, which are similar to those of trans-1,4-poly butadienes. From experiments carried out using labelled butyllithium as initiator,... 

Several workers (l. 2,3,4) have used H nmr to study the propagating chain end in the polymerization of 1,3-butadiene (1,3 BD) with a butyllithium initiator. They concluded that the poly(butadienyl) lithium chain end is virtually ICO percent 1,4 with no 1,2 structures, even though 1,2 units are incorporated in the chain. The lithium is bonded to the carbon, and there is no evidence of a T allyl type of delocalized bonding involving the Y carbon. However, the presence of vinyl in-chain units was taken as evidence for the presence of an undetectable amount of the 7 bonded chain ends in equilibrium with the bonded chain ends. Glaze and coworkers (3) further suggested that the stereochemical course of allyllithium reactions may depend on the aggregation of the reactive species. 

Poly(styrene-fe-butadiene-b-styrene) flower-like nanoparticles having a molecular weight of 56,700 Da with a polydispersity of 1.04 were prepared by Wang et al. (3) using equimolar amounts of triethylamine and butyllithium with butadiene, styrene, and divinylbenzene. 

Anionic polymerization of 2-triethylsilyl-1,3-butadiene (I) in hexane at room temperature initiated by n-, sec-, or rf-butyllithium gave high yields of ( )-l,4-poly(2-triethylsilyl-l,3-butadiene) ( -11). Neither (Z)-1,4-poly(2-tri-ethylsiIyl-1,3-butadiene) (Z-II) nor 1,2 or 3,4 units were found. The reaction is both regio- and stereospecific. 

Difunctional Initiators The methodology for preparation of hydrocarbon-soluble dilithium initiators is generally based on the reaction of an aromatic divinyl precursor with two mol of butyllithium. Unfortunately, because of the tendency of organolithium chain ends in hydrocarbon solution to associate and form electron-deficient dimeric, tetrameric, or hexameric aggregates, most attempts to prepare dilithium initiators in hydrocarbon media have generally resulted in the formation of insoluble three-dimensionally associated species [70]. The reaction of meffl-diisoprenylbenzene with 2 mol of f-butyllithium in the presence of 1 equivalent of triethylamine in cyclohexane at -20 °C has been reported to form pure diadduct without oligomerization. Equation 7.11 [71]. This initiator in the presence of 5 vol% of diethyl ether for the butadiene block has been used to prepare well-defined poly(metliyl methacrylate)- -polybutadiene-fe -poly(methyl methacrylate). 

The reaction of m-diisoproprenylbenzene with 2 moles of t-butyllithium in the presence of 1 equiv of triethylamine in cyclohexane at -20° C has been reported to form pure diadduct without oligomerization (eq. 13) (41). This initiator in the presence of 5 vol% of diethyl ether for the butadiene block has been used to prepare well-defined poly(methyl methacrylate)-6Zoc -polybutadiene-6Zoc -poly(methyl methacrylate). 

Schulz et al. investigated the homo- and eopolymerization of 2-propenyl-2-naphthalene by n-butyllithium in tetrahydrofuran at —78 °C [358,359], Homopolymerization as well as copolymerization led to quantitative yields and narrow molecular weight distributions. Molecular weights of poly(2-propenyl-2-naphthalene), determined by light scattering measurements, yielded values up to 270000gmol [358], Diblock and triblock copolymers of 2-propenyl-2-naphthalene and 1,3-butadiene were synthesized... 

Large amounts of mn -l,4-poly(2,3-dimethyl-l,3-butadiene) can be prepared by inclusion polymerization [330-332]. Urea or thiourea are used as templates. Trans-, A polymer (99 °C) is also obtained with 71-allylnickel chlorides in combination with tetrachlor-l,4-benzoquinone. Anionic polymerization by butyllithium allows good control of the products micro structure over a wide range [97]. 

It was anticipated that the copolymerization of substituted 1,1-dipheny-lethylenes with dienes such as butadiene and isoprene would be complicated by the very unfavorable monomer reactivity ratio for the addition of poly(-dienyl)lithium compounds to 1,1-diphenylethylene [133, 134]. Yuki and Oka-moto [133, 134] calculated values of ri=54 and ri=29 in hydrocarbon solutions for the copolymerization of 1,1-diphenylethylene (M2) with butadiene (Mi) and isoprene (Mi), respectively. Although the corresponding values in THE are ri(butadiene)=0.13 and ri(isoprene)=0.12, this would not be an acceptable solution since THE is known to form polymers with high 1,2-microstructures [3]. Anionic copolymerizations of butadiene (Mi) with excess l-(4-dimethyla-mino-phenyl)-l-phenylethylene (M2) were conducted in benzene at room temperature for 24-48 h using scc-butyllithium as initiator [189]. Anisole, triethy-lamine and ferf-butyl methyl ether were added in ratios of [B]/[RLi]=60, 20, 30, respectively, to promote copolymerization and minimize 1,2-enchainment in the polybutadiene units. Narrow molecular weight distribution copolymers with Mn=14xl0 to 32x10 (Mw/Mn=1.02-1.03) and 8, 12, and 30 amine... 

Teyssie and coworkers [216] have reported that the analogous initiator formed by addition of 2 moles of fcrf-butyllithium with 73, when first used to polymerize butadiene followed by low temperature polymerization of methyl methacrylate, forms poly(methyl methacrylate) end blocks that are bimodal. However, the sample used for testing was one which exhibited a broad molecular weight distribution MJMn-. 2) rather than samples prepared with this initiator which were narrow (Mw/Mn[Pg.139]

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