Butadiene initiator

Reaction between butadiene and CO2 has been extensively studied (171) since the reaction was first demonstrated (167—170). This reaction has been shown to be catalyzed by Pd (172,173), Ni (174), Ru (175), Pt (178), and Rh (172,173) catalysts. Products include gamma (5) and delta lactones (6), acids (7,8), and esters (9). Mechanistic studies have shown that butadiene initially forms a dimer (Pd, Ru, Ni) or trimer (Rh) intermediate followed by CO2 insertion (171). The fate of these intermediates depends on the metal, the ligands, and the reaction conditions. 

The observation of Tsuji et al. 148) concerned with copolymerization of 1- or 2-phenyl butadiene with styrene or butadiene illustrates again the importance of the distinction between the classic, direct monomer addition to the carbanion, and the addition involving coordination with Li4. The living polymer of 1- or 2-phenyl butadiene initiated by sec-butyl lithium forms a block polymer on subsequent addition of styrene or butadiene provided that the reaction proceeds in toluene. However, these block polymers are not formed when the reaction takes place in THF. The relatively unreactive anions derived from phenyl butadienes do not add styrene or butadiene, while the addition eventually takes place in hydrocarbons on coordination of the monomers with Li4. The addition through the coordination route is more facile than the classic one. 

Reduction of the metal dimer [CpMo(NO)l2]2 with Na/Hg in the presence of a variety of acyclic dienes generates the (diene)MoCp(NO) complexes in moderate to low isolated yield (equation 8)12,31,89. For the majority of diene ligands, complexes 60 are formed exclusively as the s-trans isomers as evidenced by NMR spectroscopy and single-crystal X-ray diffraction analysis. In comparison, complexation of the 2,3-dimethyl-l,3-butadiene initially gives a separable mixture of the s-trans (60) and s-d.v-complex (61). The s-cis isomer isomerizes to the more thermodynamically stable s-trans isomer in solution (THF, 1/2 = 5 min C6H6, ti/2 = 24 h). 

Auguste S, Edwards HGM, Johnson AF et al. (1996) Anionic polymerization of styrene and butadiene initiated by n-butyllithium in ethylbenzene determination of the propagation rate constants using Raman spectroscopy and gel permeation chromatography. Polymer 37 3665-3673... 

A styrene/butadiene initiator consisting of diisobutylaluminum hydride, triiso-butylaluminum, neodymium(III) neodecanoate, and ethylaluminum dichloride was prepared by Luo et al. (2) and used to prepare polybutadiene containing a cis-1,4-linkage content of 98.7%, a trans-1,4-linkage content of 1.0%, and a... 

For the 5000 A latex, scale-up in the 10-gal, glass-lined kettle required 64 hr polymerization at 60°C. After each addition of butadiene, initiator, surfactant, and/or mercaptan, an additional 16 hrs of polymerization was needed. Four separate additions were needed to grow the 2000 A polybutadiene latex to 5000 A. The final latex had a solids content of 25.3%... 

The radical model cannot be applied for ionic and coordination polymerizations. With a few exceptions, termination by mutual combination of active centres does not occur. The only possibility is to measure the rate of each copolymerization independently. The situation can be greatly simplified for copolymerizations in living systems. The constants ku and k22 can usually be measured easily in homopolymerizations. Also, the coaddition constants fc12 or k2] are often directly accessible when the M] and M2 active centres can be differentiated spectroscopically or when the rate of monomer M2 (M[) consumption at M] M 2 centres can be measured. Ionic equibria, association, polarity of medium and solvation must be respected, even when their quantitative effect is not known exactly. The unusual situations confronting macromolecular chemistry will be demonstrated by the example of the anionic copolymerization of styrene with butadiene initiated by lithium alkyls in hydrocarbon medium. 

The purpose of this paper is to give a brief summary of an Investigation which has been carried out into the aqueous-phase polymerisation of butadiene initiated by cobalt(III) acetylacetonate In the presence of surfactants such as sodium dodecylbenzene-sulphonate and sodium decyl sulphate. It is Intended that fuller details of the investigation will be published elsewhere in due course. 

Effect of temperature. The results for the determination of rates of polymerisation at various temperatures are summarised in Figure 11, from which it is seen that the temperature variation of rate is of the Arrhenius type. The slope of the relationship between the logarithm of the rate of polymerisation and the reciprocal of the absolute temperature corresponds to an overall activation energy of polymerisation of 15.8 kcal mole. This value is very close to that which has been reported for the aqueous -phase polymerisation of butadiene initiated by rhodium chloride(16). However, in view of the marked dissimilarity in reaction product, and therefore presumably in reaction mechanism, it seems likely... 

Polymerization of 2-triethylsilyl-l, 3-butadiene initiated by n-butyl-lithium in hexane yielded (E)-l, 4-poly(2-triethylsilyl-l, 3-butadiene). The molecular weight distribution (as determined by gel permeation chromatography) of the polymers depended on the ratio of monomer to initiator concentrations. Polymers of low polydispersity (Mu [weight-average molecular weight]/Mn [number-average molecular weight] = 1.3-1.6) and with up to 110,000 w re obtained. The... 

A similar exchange may be used to make bis-organomagnesium-halide reagents from dianionic living polymers of butadiene initiated by electron transfer from Na naphthalene ". ... 

Thus, the hydroxyl terminated polybutadiene, obtained by the radical polymerisation of butadiene initiated with hydrogen peroxide, has the following general structure [9-10, 15] ... 

The fabrication process of hydroxyl terminated polybutadiene is based on the free radical polymerisation of butadiene, initiated by hydrogen peroxide at 100-150 °C, in the presence of a solvent such as methanol [12], isopropanol [12], or in the presence of tricresyl phosphate [14]. The polymerisation in alcohols is used industrially. 

Analogous results were reported by Hay and co-workers (33, 54). In the polymerization of butadiene initiated by BuLi/TMED, the rate was found to increase with increasing TMED to lLi 2TMED, but additional TMED had no further effect. The ultraviolet spectrum of the polybutadienyl anion suggested chelating agent separated ion pairs in... 

Fig. 1. The apparatus ofAbkin and Medvedev demonstrating the long-life nature of the growing species formed in polymerization of butadiene initiated by metallic sodium...

The earliest example of living polymers was furnished by Ziegler7,23, who observed an increase in molecular weight of poly-butadiene initiated by metallic sodium on addition of fresh monomer to the system. However, it was not established whether all the polymers formed in this reaction resumed their growth or whether any residual or regenerated catalyst was left in the reactor. The latter could initiate then the formation of additional polymers. Due to these uncertainties, Ziegler s observations did not make the impact which otherwise could be expected, and did not induce further development in that field. 

Chain transfer reactions are promoted by Lewis bases. A chain transfer constant of 0.2 was reported for the telomerization of butadiene initiated by metallic sodium in a toluene/THF mixture at 40°C [116]. Such processes are used for the preparation of liquid rubbers (polybutadienes), with varying amounts of 1,2-microstructure depending on the type and amount of Lewis base, counterion, and temperature [117]. 

These observations, added to the fact that addition of polar solvents to polymerization reactions of butadiene initiated by organolithium reagents in hydrocarbon solvents can change the stereochemistry from one of predominantly rtr-1,4 to that of 1,2 and trans-, , suggests that the lithium may form a tt complex with the olefin, and if this is sufficiently strong, orient the monomer prior to the incorporation step. 

No. 16,1996, p.3665-73 ANIONIC POLYMERISATION OF STYRENE AND BUTADIENE INITIATED BYN-BUTYLLITHIUM IN ETHYLBENZENE DETERMINATION OF THE PROPAGATION RATE CONSTANTS USING RAMAN SPECTROSCOPY AND GEL PERMEATION CHROMATOGRAPHY... 

Butadiene was first prepared in 1863, and its conjugated structure was proposed in 1886 (1,2). However, the ability of butadiene to polymerize was not recognized until almost 50 years later when, in 1909, a rubbery polymer was first reported as being prepared from butadiene via thermal polymerization (3). Shortly thereafter, the more controlled poljnnerization of butadiene initiated by sodium metal was reported in 1911 (4). During this time period, a sharp rise in natural rubber prices prompted the Bayer Corp. to develop methyl rubber from... 

The microstructure of the butadiene polymer in this system has been determined by infrared spectroscopy. The vinyl content shown in Table IV was 18 to 20 percent higher in the presence of crown ether than that observed with the n-butylsodium system alone. Thus, a steady increase in the crown ether concentration showed a moderate increase in the vinyl content (68 to 80 percent) at 30 C polymerization temperature. However, we did not observe the temperature dependence of vinyl content as is typical in the polymerization of 1,3-butadiene initiated with organolithium compounds modified by polar modifiers.36 Instead, we only observed a moderate change in the vinyl content. As can be seen in Table V, the vinyl content of polybutadiene prepared by n-butylsodium/tricyclohexyl-18-crown-6 initiator decreases only from 83 percent to 70 percent as the polymerization temperature increased from 30 C to 70 C, respectively. The relatively small change of vinyl content, or 1,2 content, of polybutadiene can be interpreted as the existence of a stable complex between the allylic anion and crown ether. This would lead to less dissociation than observed with simple ethers. Thus, the microstructure of the polymer would be less sensitive to temperature. 

The living anionic polymers of protected functional methacrylate monomers herein introduced are very similar in reactivity and stability to those of MMA. Accordingly, these living polymers can initiate the polymerization of MMA, tBMA, and other protected functional methacrylate monomers, resulting in block copolymers with tailored chain structures. Complete aossover block copolymerizations among these methacrylate monomers are possible. Furthermore, living anionic polymers of styrene, a-methylstyrene, isoprene, and 1,3-butadiene initiate the polymerization of protected functional methacrylate monomers to afford well-defined AB diblock copolymers. In order to avoid ester carbonyl attack by the chain-end anions, the living anionic polymers should be end-capped with 1,1-diphenylethylene... 

Alternatively, end-functionalization of growing chains can also be obtained via transfer in chain addition polymerization. For instance, dihydroxy polybutadiene telechelics (i.e. carrying one hydroxyl group at each chain-end) are industrially produced by free radical polymerization of butadiene initiated by hydrogen peroxide which simultaneously gives rise to transfer reactions ... 

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