Anionic polymerization of butadiene

Other Organolithium Compounds. Organoddithium compounds have utiHty in anionic polymerization of butadiene and styrene. The lithium chain ends can then be converted to useflil functional groups, eg, carboxyl, hydroxyl, etc (139). Lewis bases are requHed for solubdity in hydrocarbon solvents. 

A pilot scale plant, incorporating a three litre continuous stirred tank reactor, was used for an investigation into the n-butyl lithium initiated, anionic polymerization of butadiene in n-hexane solvent. The rig was capable of being operated at elevated temperatures and pressures, comparable with industrial operating conditions. 

Polymer Synthesis and Characterization. This topic has been extensively discussed in preceeding papers.(2,23,24) However, we will briefly outline the preparative route. The block copolymers were synthesized via the sequential addition method. "Living" anionic polymerization of butadiene, followed by isoprene and more butadiene, was conducted using sec-butyl lithium as the initiator in hydrocarbon solvents under high vacuum. Under these conditions, the mode of addition of butadiene is predominantly 1,4, with between 5-8 mole percent of 1,2 structure.(18) Exhaustive hydrogenation of polymers were carried out in the presence of p-toluenesulfonylhydrazide (19,25) in refluxing xylene. The relative block composition of the polymers were determined via NMR. 

Hence measurements have been made on unsubstituted allyl alkali-metal compounds, and also on neopentylallyl (I, 5,5-dimethylhexen-2-) and neopentylmethallyl (II, 2,5,5-trimethyl-hexen-2-) alkali-metal compounds which are models of the polymerizing chain end in the anionic polymerization of butadiene and isoprene respectively. 

Richardson and Sacher (41) showed that the anionic polymerization of butadiene with ethyllithium in THF produces mainly 1.2 structure in the polybutadiene. Roha (2) reviewed the typical anionic polymerization of butadiene to polymers containing 1.2 structure by catalysts such as alkyl sodium and alkyl potassium. Sodium naphthalene with THF produces 88% 1,2 polybutadiene (42). 

The alkylmetal-metal alkoxide combination was first described by Morton [6] for the anionic polymerization of butadiene - addition of an equivalent of sodium iso-propoxide improved the catalytic activity of allylsodium. Fifteen years later the spe-... 

Polymers with specific end groups can be prepared by deliberately introducing particular reagents that kill living polymers. Thus in the anionic polymerization of butadiene with bifunclional initiators, carboxyl end groups are produced by termination with CO ... 

Additionally, if the initiation reaction is more rapid an the chain propagation, a very narrow molecular weight distribution, MJM = 1 (Poisson distribution), is obtained. Typically living character is shown by the anionic polymerization of butadiene and isoprene with the lithium alkyls [77, 78], but it has been found also in butadiene polymerization with allylneodymium compounds [49] and Ziegler-Natta catalysts containing titanium iodide [77]. On the other hand, the chain growth can be terminated by a chain transfer reaction with the monomer via /0-hydride elimination, as has already been mentioned above for the allylcobalt complex-catalyzed 1,2-polymerization of butadiene. 

The highly nucleophilic character of delocalized organometallics towards carbon-carbon double bonds is the origin of the anionic polymerization of butadiene, isoprene, and styrene [10-12]. This is the major industrial application of organolithi-... 

By the anionic polymerization of butadiene and the functionalization of the active ends of the polymer by formaldehyde or ethylene oxide ... 

As these anions are not reactive enough to continue propagation, the chains are effectively terminated. By adding a proton donor subsequently to the polymerization system, the peroxy and carboxyl anions are converted to OH and COOH groups. A notable example of the application of the latter reaction is the preparation of carboxyl ion terminated polybutadiene by anionic polymerization of butadiene with bifunctional initiators, followed by termination with CO2 ... 

One of the major areas for potential involves the synthesis of polyolefin block copolymers. A PP-EPR-PP or PE-EPR-PE block copolymer could have large potential as is or in blends with other polyolefins. PE-EPR-PE block copolymers have been synthesized via anionic polymerization of butadiene-isoprene-butadiene ABA block copolymers followed by hydrogenation [Mohajer et al, 1982 Rangarajanout et al., 1993]. These materials would have utility in hot melt adhesive formulations as well as general-purpose thermoplastic elastomer applications. Improvements on the synthesis procedures to offer viable approaches to polyolefin block copolymers could open up a new class of commercial polyolefins. In summary, several opportunities exist for new combinations of commercial blends from the list of commodity polymers. 

Metalated PIB obtained by one-pot dehydrochlorination-metalation of tert chlorine-ended PIB by potassium-t-amylate/nBuLi and tBuOK/nBuLi mixtures was used to initiate the anionic polymerization of butadiene resulting PIB-polybutadiene block copolymers. ... 

Anionic polymerization of butadiene, followed by hydrogenation, provides a route to compositionally homogeneous materials similar in structure to ethylene/1 -butene copolymers. The copolyma- composition can be varied by addition of polar modifiers to the polymerization mixture, thus generating materials with differing mole fractions of 1,2 addition, jCjj. 

A tadpole polybutadiene with two linear PS chains has been prepared by Quirck and Ma living anionic poly(styryl) lithium chains were first coupled by reacting the living ends with the double diphenylethylene. Then the resulting polymer bearing two reactive catbanionic centers located in the middle of the chain was used as a bifimcdonal macroinitiator to initiate the anionic polymerization of butadiene. The two... 

Developments in the anionic polymerization of butadiene were adopted for manufacture of solution SBR. While the emulsion process gave primarily 1,4-cis microstructure in the final product, the solution process gave a lower level of 1,4-cis level, typically around 45%. Furthermore the cis content as well as 1,2-vinyl content could be modified. In addition, better control of branching and molecular weight distribution attainable with anionic process made solution SBR suitable for tire applications, challenging the established use of cold SBR. Developments in the anionic process also led to new copolymer structures in which blocks of polybutadiene can be coupled to blocks of polystyrene, generating a imique class of polymers. Developments in SB block copolymers led to new materials which were thermoplastic in character, unlike SBR which is an elastomer. Solution-processes-based thermoplastic SB block copolymers form the basis of the transparent impact polystyrene (TIPS) as well as the other block copolymers used in plastics modification. The block copolymers of styrene and butadiene are the subject of the second part of this article. 

The MXM block copolymers were prepared by sequential anionic polymerization of butadiene, styrene and methyl methacrylate with the diadduct of t-BuLi onto m-diisopropenylbenzene (nt-DlB) as a difiinctional initiator. The MB diblock copolymer was prepared in the same way except for a monofimctional initiator. Details on the... 

Rodriguez-Guadairama LA. Application of online near infrared spectroscopy to study the kinetics of anionic polymerization of butadiene. Eur Polym J 2007 43 928-937. 

In 1997, before Bayer reached the commercial stage with their HTPBD, direct competition emerged with the introduction of HTPBD produced by anionic polymerization of butadiene. This material was developed by the Czech company Kaucuk and was marketed under the trade name Krasol . The lower feedstock cost of butadiene versus cyclooctadiene gave Krasol a cost advantage in this already cost-disadvantaged specialty polyurethane market segment. Bayer abandoned its line of ROMP-derived HTPBD before a commercial launch, whereas Krasol was successfully commercialized and is now marketed by Cray Valley. 

In particular, of importance is the use of anionic polymerization to obtain polydienes. Depending on the type of used catalyst and on operating conditions one can obtain in this way polydienes of different stmc-tures, including polymers with overwhelming cis-, 4 structure, similar to that of natural rubber. The influence of the used catalyst on the course of anionic polymerization of butadiene and isoprene and the structure of formed polymers are given in Table 8.7. 

TABLE 8.7 Effect of Catalyst in Anionic Polymerization of Butadiene and Isoprene on the Structure of the Resulting Polymer Chain... 

On the topic of statistical copolymer crystallization, the scope of the review will be limited to composition-ally homogeneous statistical copolymers. In many studies, anionic polymerization of butadiene, followed by hydro-... 

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