Polymerization conjugated dienes

Monomers that copolymerize with thiocarbonyl fluoride include olefins, vinyl halides, vinyl esters, ally esters, acrylates, vinyl ethers, and vinyltrichloro-silane. Nonconjugated diolefins lead to crosslinked products. Conjugated dienes inhibit polymerization. 

Title Modified Conjugated Diene Polymer, Polymerization Intitiator, Method of Producing the Same, and Rubber Composition... 

Modified Conjugated Diene Polymer, Polymerization Intitiator... 

The acid-catalyzed hydrocarboxylation of olefins (the Koch reaction) can be performed in a number of ways.565 In one method, the olefin is treated with carbon monoxide and water at 100 to 350°C and 500 to 1000 atm pressure with a mineral-acid catalyst. However, the reaction can also be performed under milder conditions. If the olefin is first treated with CO and catalyst and then water added, the reaction can be accomplished at 0 to 50°C and 1 to 100 atm. If formic acid is used as the source of both the CO and the water, the reaction can be carried out at room temperature and atmospheric pressure.566 The formic acid procedure is called the Koch-Haaf reaction (the Koch-Haaf reaction can also be applied to alcohols, see 0-103). Nearly all olefins can be hydrocarboxylated by one or more of these procedures. However, conjugated dienes are polymerized instead. 

The conjugated dienes can polymerize in four modes cis 1,4-, trans 1,4-, 1,2- and 3,4-, the latter pair being equivalent in the absence of appropriate substitution. Early workers relied entirely upon IR spectroscopy to analyze the concatenation in their polymers. There are a number of problems associated with the technique correct assignment of peaks, the additivity and the inherent insensitivity arising from the smallness of the extinction coefficients of double bonds bearing more than one substituent (such as arises from 1,4-enchainment). In consequence, the reliability of much of the early work is uncertain the advant of NMR spectrometers has,... 

The structure of the polymer obtained in the polymerization of butadiene and isoprene with heterogeneous Ziegler-Natta catalysts depends on the nature of the monomer, catalyst system, and reaction conditions. Previously reported results are reviewed and a mechanism is proposed for the stereoregulated polymerization of conjugated dienes. The polymerization of cyclopentadiene with LiAlH -TiCl4 or LiAlR4-TiCl4 catalyst system yields a readily oxidized polymer for which a 1,2-structure is proposed. 

Conjugated dienes are polymerized by n-BuCal (in admixture with n-Bu2Ca) by a typical anionic addition mechanism at 20°-50°C. Initiation by addition is slow compared to the subsequent polymerization, and the microstructure of the polymer is solvent dependent. Polybutadiene with predominantly trans-1,4 links (48-72%) is obtained in hydrocarbons or Et20, but 1,2-polymerization is promoted in THE or by addition of hexamethylphosphoramide (HMPA). Polymerization of butadiene by PhjCMX (M = Ca, Sr, Ba X = Cl, Br) at — 10°C in THE yields polymer with increasing... 

In addition to the configurational isomerism encountered in polymers derived from asymmetric olefins, geometric isomerism is obtained when conjugated dienes are polymerized, e.g., (CH2=CX—CH=CH2). Chain growth from monomers of this type can proceed in a number of ways, illustrated conveniently by 2-methyl-1,3-butadiene (isoprene). Addition can take place either through a 1,2-mechanism or a 3,4-mech-anism, both of which could lead to isotactic, syndiotactic, or atactic structures, or by a 1,4-mode leaving the site of unsaturation in the chain. 

Conjugated dienes upon polymerization would result in either cis or trans isomeric polymer. One of the most important examples of this class is isoprene. Example of these isomeric polymers is shown in Scheme 3.9. 

Conjugated diene polymerization n. Conjugated dienes often polymerize as bi-functional monomers with 1,4 addition or 1,2 addition. In this process, one double bond remains in the main chain for each monomer. 

Divinyl polymerization, polymers n. Polymerization of a monomer, which contains two vinyl groups. When the two double bonds are conjugated (as in 1,3-dienes) the polymerization is called diene polymerization. 

Section 10.8.3 in Chapter 10 showed several reactions of the C=C unit of alkenes that give polymers. Dienes undergo polymerization reactions, but the presence of the second double bond leads to some interesting reactions. Radical initiated polymerization reactions of alkenes were discussed in Chapter 10 (Section 10.8.3) this section will focus on the radical-initiated polymerization of conjugated dienes. 

Unlike polyethylene and other simple alkene polymers, natural rubber is a polymer of a conjugated diene, isoprene (2-methylbuta-l,3-diene). The polymerization takes place by 1,4-addition of isoprene monomer units to the growing chain, leading to formation of a polymer that still contains double bonds spaced regularly at four-carbon intervals. As the following structure shows, these double bonds have Z stereochemistry ... 

Conjugated Diene Polymerization n Conjugated dienes often polymerize as bi-functional monomers... 

LB Films of Polymerizable Amphiphiles. Stxidies of LB films of polymerizable amphiphiles include simple olefinic amphiphiles, conjugated double bonds, dienes, and diacetylenes (4). In general, a monomeric ampbipbile can be spread and polymerization can be induced either at tbe air—water interface or after transfer to a soHd substrate. Tbe former polymerization results in a rigid layer tbat is difficult to transfer. 

The discovery by Ziegler that ethylene and propylene can be polymerized with transition-metal salts reduced with trialkyl aluminum gave impetus to investigations of the polymerization of conjugated dienes (7—9). In 1955, synthetic polyisoprene (90—97% tij -l,4) was prepared using two new catalysts. A transition-metal catalyst was developed at B. E. Goodrich (10) and an alkaU metal catalyst was developed at the Ekestone Tke Rubber Co. (11). Both catalysts were used to prepare tij -l,4-polyisoprene on a commercial scale (9—19). 

Conjugated dienes can be polymerized just as simple alkenes can (Section 7.10). Diene polymers are structurally more complex than simple alkene polymers, though, because double bonds remain every four carbon atoms along the chain, leading to the possibility of cis-trans isomers. The initiator (In) for the reaction can be either a radical, as occurs in ethylene polymerization, or an acid. Note that the polymerization is a 1,4-addition of the growing chain to a conjugated diene monomer. 

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