Anionic polymerization of isoprene

A polymer-bound hindered amine light stabilizer [P-HALS] has been synthesized by terminating the living anionic polymerization of isoprene with 4(2,3-epoxy pro-poxy)-1,2,2,6,6-pentamethylpiperidine followed by hydrogenation of the resulting polymer to E-P copolymer using Zeigler type catalyst [40] ... 

Synthetic cA-l,4-polyisoprene (structure 5.42) is produced at an annual rate of about 100,000 t by the anionic polymerization of isoprene when a low dielectric solvent, such as hexane, and K-butyllithium are used. But, when a stronger dielectric solvent, such as diethy-lether, is used along with w-butyllithium, equal molar amount of tra i -l,4-polyisoprene and cA-3,4-polyisoprene units is produced. It is believed that an intermediate cisoid conformation assures the formation of a cis product. An outline describing the formation of cA-1,4-polyisoprene is given in structure 5.42. 

A polymer similar to natural hevea rubber is obtained using the anionic polymerization of isoprene under these conditions. In more polar solvents employing sodium and potassium initiators the amount of cA-1,4 units decreases and trans-, A and trans- i,4 units predominate. 

TABLE 8-10 Effect of Solvent and Initiator Concentration on Stereochemistry in Anionic Polymerization of Isoprene at 20° Ca... 

Anionic Polymerization of Isoprene by the Complexes Oligoisoprenyllithium/Tertiary Polyamines in Cyclohexane. I. Kinetic Study... 

HAY et al (12, 13) showed that the addition of TMEDA to butyl-lithium (BuLi) produces a remarkable increase in reactivity toward the polymerization of butadiene. This higher reactivity is attributed to the absence of association of alkyllithium species and the presence according to the maximum rate of polymerifcftr-tion, of a separated ion pair during the polymerization. ERUSSALIMSKY et al(14) described the anionic polymerization of isoprene in the presence of TMEDA. They showed that the tertiary diamine causes a significant increase of the polymerization rate and of the content of 3,4-links in the polymers formed, a plateau being reached for r = TMEDA/living species =4. 

The data under discussion were obtained in the course of a study of the anionic polymerization of isoprene in benzene at 35.1° C. Earlier work on the polymerization using -butyl lithium as initiator in a number of hydrocarbon solvents had shown that the kinetic behaviour was complicated. For example, the isoprene concentration-time curves were sigmoidal and the ratio of the number of moles of isoprene consumed to the number of moles of n-butyl lithium reacted increased as the reaction proceeded. These and other complications showed that the rate of the reaction could not possibly be represented by an equation of the type... 

A transformation method can introduce some functional groups at the junction as in B-63, which bear a fluorescent dye between the polyisoprene and polystyrene segments.375 The preparation is based on quenching the living anionic polymerization of isoprene with l-(9-phenanthryl)-l-phenylethylene followed by addition of excess a,a -dibromo-/>xylene, which affords a C—Br terminal effective for the copper-catalyzed radical polymerization of styrene. 

Since rate constants for.PVL In acetonitrile or DMSO are the same or higher than those of ormethyl-or-propylproplolactone, the polymerization rate of PVL In THF should be Just as high as that of the methyl, propyl derivative. If this Is so, the above data suggest anionic polymerization of PVL proceeds as fast as anionic polymerization of Isoprene In hydrocarbons to cls-1,4-polyIsoprene. This Is Indeed quite Impressive. 

It is also possible to form block co-polymers via the living anionic ROP of the phosphorus-bridged ferrocenophanes (Section 12.06.3.3.3). " Diblock co-polymers such as PI-/)-PFP 108 can be prepared by the sequential anionic polymerization of isoprene and ferrocenophane 107 (Scheme 10). These materials yield spherical micelles in -hexanes with an amorphous PFP core and a PI corona. The PI corona can be cross-linked via radical reactions to yield a permanently cross-linked shell, which retains its integrity even in good solvents for both blocks. With PFP block co-polymers the possibility of the coordination of various catalytically active transition metal moieties to the phosphorus centers may prove useful for catalysis and for materials science applications. 

Hydrocarbon Solvents One of the most important synthetic and commercial aspects of anionic polymerization is the ability to prepare polydienes [poly(l,3-dienes)] with high 1,4-microstructure using lithium as the counterion in hydrocarbon solutions [3, 156]. The key discovery was reported in 1956 by scientists at the Firestone Tire and Rubber Company that polyisoprene produced by lithium metal-initiated anionic polymerization had a high (>90%) cm-1,4-microstructure similar to natural rubber [47], In general, conjugated 1,3-dienes [CH2=C(R)-CH=CH2] can polymerize to form four constimtional isomeric microstructures as shown below. The stereochemistry of the anionic polymerization of isoprene and... 

Bywater, S., Worsfold, D.J., 1967b. Anionic polymerization of isoprene ion and ion-pair contributions to polymerization in tetrahydrofuran. Can. J. Chem. 45 (16), 1821-1824. 

CHAPTER 3 9. Discuss steric control in homogeneous anionic polymerization of isoprene in nonpolar solvents. 

Figure 2 The triblock terpolymer PI-b-PCEMA-b-Pf BA and TEM images of cylindrical micelles and nanotubes thereof (the anionic polymerization of isoprene was performed in dry hexane the micelles were stained with OSO4 and the nanotubes with RUO4). Reproduced with permission from Stewart, S. Liu, G. Angew. Chem. hit. Ed. 2000,39,340-344. ...

Anionic polymerization of isoprene was carried out using practically the same method as reported by Rubio and by Morton et al. The bifunctional initiator, 2,4-hexadienyl dilithium was prepared through the reaction of trans,trans-2,4-hexadiene with Li metal in triethylamine. 

The polyisoprene (PI) samples were obtained from anionic polymerization of isoprene (Fig. 1). According to the supplier. Polymer Source, the sample is linear (no ramification) and its micro-composition is 80% cis, 15% trans and 5% other 1. We are working with the isomer cis that have a net end-to-end polarization vector. Before the experiments samples were dried in a vacuum oven at 70 zC for 24 hours to remove any trace of solvent. 

PSt -co-PCMS copolymers were synthesized via the same procedure as shown in Scheme 3.44. The reactivity ratio of CMS St for the LFRP is evidently the same as for conventional radical polymerization, and the chlorine atoms are randomly distributed along the PSt backbone. The coupling reaction of PSt-co-PCMS with an excess of about 50% DPE-terminated polyisoprenylithium, which was prepared by anionic polymerization of isoprene with BuLi as initiator, followed by termination upon addition of DPE into the polymerization... 

Sequential anionic polymerization of isoprene, styrene, isoprene, 4-(vinylbenzyl)dimethylamine, and isoprene ABACA pentablock terpolymers (ISIAI) with blocks of similar lengths was published in the early 1980s by Fujimoto s group.They studied the influence of the solvent qirality on the morphology and found lamellar stmctrrres for benzene and dioxane (both are considered to be rather nonselective solvents), while for cyclohexane a poorly ordered stmcture of PS spheres in a matrix of the other components was found, due to the bad solubility of PS in cyclohexane. 

Starting with a functionaUzation of a,(o-dihydroxy-terminated poly(ethylene oxide) or poly(propylene oxide) by HDl 18, followed by a reaction with a,(0-diamino-terminated copolymer of butadiene and acrylonitrile, a triblock macroactivator was synthesized the anionic polymerization of CL at 140 °C in the presence of this copolymer gave an A-B-C-B-A copolymer [61]. A similar macroactivator for block copolymer synthesis was prepared by a stepwise anionic polymerization of isoprene (with dilithium a-methylstyrene tetramer) and oxirane [62]. 

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