Polybutadiene, synthesis

Catalytic Hydrogenation, Hydroformylation, and Hydroxymethylation of Polybutadiene Synthesis and Characterization... 

On the basis of experimental molecular-mass distributions of the polymers, the inverse task was solved via Tikhonov s regularization method [3] as a result, the functions of distribution of active sites over the probability of chain termination were obtained (Fig. 4.3,4.4). The titanium catalytic system is characterized by a polymodal distribution function, where each maximum corresponds to a certain type of polymerization sites. Under our conditions of polybutadiene synthesis, there are four types of active sites that form macromolecules with the following most probable molecular masses InM = 9.2-10.4 (I), 11.2-11.4 (II), 12.9-13.2 (III), and 14.1-14.7 (IV) (Fig. 4.3). The position of maxima on the curves is conversion independent. This implies that each type of site forms macromolecules of a certain length throughout the process. 

Butadiene is by far the most important monomer for synthetic rubber production. It can be polymerized to polybutadiene or copolymerized with styrene to styrene-butadiene rubber (SBR). Butadiene is an important intermediate for the synthesis of many chemicals such as hexa-methylenediamine and adipic acid. Both are monomers for producing nylon. Chloroprene is another butadiene derivative for the synthesis of neoprene rubber. 

Synthesis and Characterisation of Hydroxy-Terminated Polybutadienes , Report No 6/R/66, ERDE, Waltham Abbey, Essex (Engl) (1967)... 

Pryke, A. et al. Synthesis, hydrogenation, and rheology of 1,2-polybutadiene star polymers. Macromolecules, 35, 467, 2002. 

Polymeric polyolefins, such as polybutadiene, secondary amines, and synthesis gas, are reacted in the presence of a catalyst system comprising a ruthenium-containing compound, a rhodium-containing compound, a steri-cally hindered phosphine, and a solvent [1191]. Preferred polybutadiene feedstocks are those with a predominance of main chain, rather than pendant olefin groups and in particular, those polymers containing both the 1,2-polybutadiene and 1,4-polybutadiene units. These polymers of high amine content are useful as down-hole corrosion inhibitors. 

Polybutadiene (PB) and polyisoprene with cis-trans controlled microstructure (synthesis of "natural rubber"). 

Recent advances in the synthesis of crystallizable elastomers based on high cistactic and transtactic polybutadiene structures are reviewed. 

In particular, the increase of tacticity and the possibility of achieving the synthesis of "all cis" diene copolymers of high molecular weight allows the possibilities of broadening the range of products attainable in conventional, solution polybutadiene plants,... 

Since the anionic triblock copolymers are based on monomers susceptible to this mechanism, one recent approach to this synthesis has been to prepare butadiene-isoprene-butadiene triblock copolymers, which are then hydrogenated so that the high-1,4 polybutadiene end blocks become crystallizable, similar to high-pressure polyethylene (l -5 ). 

The trans/cis ratio of the product must, therefore, be determined at an earlier reaction stage and most probably by the ratio of species 27a and 27b. Steric or electronic factors affecting this ratio will influence the trans/cis ratio of the resulting 1,4-hexadiene. The phosphine and the cocatalyst effect on the stereoselectivity can thus be interpreted in terms of their influence on the mode of butadiene coordination. Some earlier work on the stereospecific synthesis of polybutadiene by Ni catalyst can be adopted to explain the effect observed here, because the intermediates that control the stereospecificity of the polymerization should be essen-... 

In the polymerization of butadiene, Teyssie (52-54) has shown that certain electron donors, such as alcohols or phosphines, can convert tt-allylnickel chloride from a catalyst which forms c/j-polybutadiene to one which produces frans-polybutadiene. These ligands presumably block a site on the nickel atom, forcing the butadiene to coordinate by only one double bond. While alcohols cannot be added directly to the hexadiene catalyst (as they deactivate the alkylaluminum cocatalysts), incorporation of the oxygen atom on the cocatalyst places it in an ideal position to coordinate with the nickel. The observed rate reduction (52) when the cri-polybutadiene catalyst is converted into a fra/w-polybutadiene catalyst is also consistent with the observed results in the 1,4-hexadiene synthesis. 

We chose the tt-bonds of the polybutadiene block as the functional groups to connect different side groups to the polymer block. A direct connection of side groups to the rr-bonds is difficult and leads to unstable products therefore, a two-step synthesis was employed. The first step is a conversion of the Jt-bonds into a more easily accessible species. This can be done by either hydroxylation (hydro-... 

The synthesis of block copolymers with blocks of ultralow cohesion energy densities on the basis of polystyrene-6-polybutadiene via two highly efficient polymer analogous reactions has been presented. 

Polybutadiene (PB), 9 558 14 246 24 703 commercial block copolymers, 7 648t oxygen permeability at 25°C, 3 400 physical properties of, 4 376t in rubber compounding, 21 764-765 synthesis, 4 375-377 in tire compounding, 21 807 nel-Polybutadiene, 7 610t Polybutadiene-based urethane sealants, 22 36... 

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... 

Uses Synthetic rubbers and elastomers (styrene-butadiene, polybutadiene, neoprene) organic synthesis (Diels-Alder reactions) latex paints resins chemical intermediate. 

Research efforts are ongoing into the use of dinitrogen pentoxide for the industrial synthesis of nitrated hydroxy-terminated polybutadiene (NHTPB) from epoxidated HTPB (Section 3.10). The reaction of aziridines with dinitrogen pentoxide is an important route to 1,2-nitramine-niU ates and these reactions are discussed in Section 5.8.1. ... 

The synthesis of nitrated hydroxy-terminated polybutadiene (NHTPB) (44) from the reaction of partially epoxidized hydroxy-terminated polybutadiene with dinitrogen pentoxide... 

Initial reports on chemoenzymatic block copolymer synthesis focus on the enzymatic macroinitiation from chemically obtained hydroxy-functional polymers (route A in Fig. 4). The first report on enzymatic macroinitiation was published by Kumar et ah, who used anionically synthesized hydroxy-functional polybutadiene of various molecular weights ranging from 2600 to 19,000Da (Fig. 5) [16]. In a systematic study, the authors investigated the efficiency of the macroinitiation of CL and PDF by Novozym 435 as a function of the polybutadiene macroinitiator. The reaction profile showed that polybutadiene consumption steadily increased with the reaction... 

Fig. 5 Synthesis of poly(butadiene- -caprolactone) from hydroxy-functional polybutadiene [16]...

Microstructure of Polybutadienes. Microstructure strongly influences the viscosity of the CTPB prepolymer. The viscosity of CTPB increases with increased vinyl content, but for CTPB prepolymers of the required molecular weight, an upper limit of 35% vinyl groups is satisfactory from the standpoint of propellant processing characteristics. It has also been found that the microstructure changes markedly with the synthesis process. Lithium-initiated polymerization yields prepolymers with slightly higher vinyl content than those produced by free radical initiation. 

The successful synthesis of such materials requires that, Initially, telechelic tertiary amine terminated polybutadiene be prepared quantitatively. Alternative routes are therefore being sought, two of which are outlined In this paper. 

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