Polymerization of Other Monomers

A similar but direct electron transfer from the metal to the monomer is operative when alkali and alkaline-earth metals (e.g., sodium) are used as the initiator.169,173,177 In this case, however, initiation is slow relative to propagation because of the low metal surface area available, and this method is used only for special purposes. 1,1-Dipehylethylene, for example, forms a dianion that, for steric reasons, is not capable for further head-to-tail addition of the monomer, but it can be used to initiate the polymerization of other monomers.178... 

On the basis of the polarographic studies, the direct electron transfer polymerizations of the monomers, of which half-wave potentials could be measured, were conducted keeping the potential at a level where the monomer alone was reduced and the electrolyte was not affected. During the electrolysis of a-methyl-styrene, for example, the red color of the carbanion was observed around the cathode, but dissipacted and vanished quickly. Only low polymers were found in the cathodic compartment, but no polymer in the anolyte. In the polymerization of other monomers almost identical results were obtained. From the fact that tri-n-butyl-amine was detected in the catholyte and analysis of the end group of polymers obtained, two possible termination steps were postulated ... 

Anionic ring-opening polymerization of l,2,3,4-tetramethyl-l,2,3,4-tetraphenylcyclo-tetrasilane is quite effectively initiated by butyllithium or silyl potassium initiators. The process resembles the anionic polymerization of other monomers where solvent effects play an important role. In THF, the reaction takes place very rapidly but mainly cyclic live- and six-membered oligomers are formed. Polymerization is very slow in nonpolar media (toluene, benzene) however, reactions are accelerated by the addition of small amounts of THF or crown ethers. The stereochemical control leading to the formation of syndiotactic, heterotactic or isotactic polymers is poor in all cases. In order to improve the stereoselectivity of the polymerization reaction, more sluggish initiators like silyl cuprates are very effective. A possible reaction mechanism is discussed elsewhere49,52. 

Living species may be converted into dead ones by addition of a molecule with a mobile hydrogen atom (water, alcohol, etc.). Termination may also be performed by electrophilic molecules and in that case polymers are terminated by functional groups that can be used to initiate the polymerization of other monomers or as coupling adents between macromolecular chains. 

Another type of one-end reactive oligomers are oligomeric initiators which have an end group capable of initiating the polymerization of other monomers. Polymeric azo compounds of the type 52 and 53 were prepared by reaction of anionic living polymers with azo-bis-isobutyronitrile 9) ... 

The end-hydroxy oligomer may serve as an end-initiator oligomer when it is transformed into an initiating catalyst of ring-opening polymerization of other monomers. For example, end-hydroxy oligomers were converted into metal aldoxides 54 which functioned as a catalyst in the living polymerization of e-caprolactone (CL)50). 

It would be naive to even consider the principles of propagation controlled by ion pairs and free ions as being clarified. Nevertheless, a lot has been done, and the mosaic is being filled in, step by step. Important findings were also recorded with polymerizations of other monomers. 

Davtyan et al. analyzed the problem of changes mass distribution with conversion during the polymerization of heterocycles [58], This case is interesting the question of the coexistence of one or two active centres on a single growing macromolecule is solved by means of rate equations. The results can also be applied to polymerizations of other monomers, when the conditions... 

The detailed mechanisms of cyclization in the polymerization of other monomers may be similar to this one or slightly different. For aU these sterns, however, the final equilibrium can be described by a formal schai in which a linear polymer s -ment is convated into a macrocyclic segment togetha with a correspondingly short-er, linear segment ... 

In contrast to the above situations, parylene polymer deposition has very poor adhesion to a smooth surface substrate but can penetrate deep into small cavities. para-Xylylene prefers to react with another para-xylylene or its derivatives. Although it has the feature of difunctional free radical, it is rather stable and does not initiate polymerization of other monomers for conventional free radical polymerization. In spite of numerous attempts, the polymerization of various vinyl monomers initiated by para-xylylene or copolymerization of vinyl monomers with /7ura-xylylene has been elusive. 

Polymers with LM in side groups can also be obtained by polymerization of other monomers. Thus, poly(ethylene oxide) containing LM (Table 1 LMg) is formed by copolymerization of ethylene oxide and 9-anthryaldehyde in the presence of a modified organoaluminum catalyst ... 

TEMPO, />substituted TEMPO based alkoxyamines 3, and compounds such as 4, 5, and 7 have been applied successfully for polymerizations of styrene, substituted styrenes, and 4-vinylpyridine, and some copolymerizations and block copolymerizations were reported. However, living and controlled radical polymerization of other monomers, especially acrylates, require the use of the more recently developed structures 6, 8, or 9. These also yield well-controlled and living block copolymers, but methacrylates have so far resisted all efforts to obtain large conversions. Undoubtedly, many failures are due to unfavorable rate constants or side reactions. 

It is now clear that the advent of single-site catalysts for the stereoselective polymerization of olefins has initiated a revolution in polymer synthesis. Although the vast majority of homogeneous polymerization catalysts are designed for olefin polymerization, the extension of this area of catalysis for the polymerization of other monomers, such as lactones and epoxides, is already in progress. 

Let us briefly summarize the state of the art in the polymerization of other monomer groups in the presence of polymer-boxmd metal complexes. Considerable progress has been achieved in polymerization of dienes, namely, butadiene and isoprene, catalyzed by macromolecnlar complexes based on rare earth halides [114], Co-oligomerization of 1,3-butadiene and CO2 with immobilized palladium complexes (phosphynated PS as macromolecnlar ligand) [115] and polymerization of acetylene monomers with immobilized complexes of Mo(V), W(VI), and Pd(II) have been developed though they have not been investigated intensively. 

Uses Intermediate for prod, of vinylcyclohexene dioxide comonomer in polymerization of other monomers in halogenation to polyhalogenated derivs. used as flame retardants prod, of insecticides with ethylene chlorohydrin organic synthesis Manuf./Distrib. Aldrich http //www.sigma-aldrich.com, Fluka http //www.sigma-aldrich.com, Sigma... 

The Xmax data in Fig. 4.1 are remarkable in that polystyrene is considered to be the archetype of a polymer which is insoluble in SCCO2 [7j. The results are indicative of the significant solvent power of the monomer which is present in the reacting styrene-polystyrene-scC02 mixtures. It may be expected that polymerizations of other monomers or copolymerizations of styrene with other monomers may be carried out in homogeneous phase up to high monomer conversion. Styrene-... 

Vinyl polymerization with initiator-transfer reagent-terminator (iniferter) is interesting as a living polymerization model, in which a reversible combination of polymer radicals with stable primary radicals occurs continuously during the polymerization " . The resulting telechelic polymers initiated the polymerization of other monomers to give block copolymers in good yields... 

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