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Ring opening polymerization, cyclic ethers

Cyclic amino-carbenes, in molybdenum carbonyls, 5, 457 Cyclic bis(phosphine) dichlorides, with iron carbonyls, 6, 48 Cyclic carbenes, as gold atom ligands, 2, 289 Cyclic carbometallation, zirconium complexes, 10, 276 Cyclic carbozirconation characteristics, 10, 276 intermolecular reactions, 10, 278 intramolecular reactions, 10, 278 Cyclic dinuclear ylides, and gold , 2, 276 Cyclic 1,2-diols, intramolecular coupling to, 11, 51 Cyclic enones, diastereoselective cuprate additions, 9, 515 Cyclic esters, ring-opening polymerization, via lanthanide catalysis, 4, 145 Cyclic ethers... [Pg.88]

The key initiation step in cationic polymerization of alkenes is the formation of a carbocationic intermediate, which can then interact with excess monomer to start propagation. We studied in some detail the initiation of cationic polymerization under superacidic, stable ion conditions. Carbocations also play a key role, as I found not only in the acid-catalyzed polymerization of alkenes but also in the polycondensation of arenes as well as in the ring opening polymerization of cyclic ethers, sulfides, and nitrogen compounds. Superacidic oxidative condensation of alkanes can even be achieved, including that of methane, as can the co-condensation of alkanes and alkenes. [Pg.102]

Cyclic ether and acetal polymerizations are also important commercially. Polymerization of tetrahydrofuran is used to produce polyether diol, and polyoxymethylene, an excellent engineering plastic, is obtained by the ring-opening polymerization of trioxane with a small amount of cycHc ether or acetal comonomer to prevent depolymerization (see Acetal resins Polyethers, tetrahydrofuran). [Pg.246]

Quite often in the ring-opening polymerization, the polymer is only the kinetic product and later is transformed to thermodynamically stable cycles. The cationic polymerization of ethylene oxide leads to a mixture of poly(ethylene oxide) and 1,4-dioxane. In the presence of a cationic initiator poly(ethylene oxide) can be almost quantitatively transformed to this cyclic dimer. On the other hand, anionic polymerization is not accompanied by cyclization due to the lower affinity of the alkoxide anion towards linear ethers only strained (and more electrophilic) monomers can react with the anion. [Pg.86]

Formation of cyclic oligomers is a characteristic feature of the cationic ring-opening polymerization of cyclic ethers (16-17). [Pg.199]

The cationic ring-opening polymerization of cyclic ethers has been the subject of many recent investigations (1.. Nuclear magnetic resonance (NMR) methods, particularly carbon-13 techniques, have been found most useful in studying the mechanism of these polymerizations ( ). In the present review we would like to report some of our recent work in this field. [Pg.237]

In addition to step and chain polymerizations, another mode of polymerization is of importance. This is the ring-opening polymerization (ROP) of cyclic monomers such as cyclic ethers, acetals, amides (lactams), esters (lactones), and siloxanes. Ring-opening polymerization is of commercial interest in a number of systems, including the polymerizations of ethylene oxide... [Pg.544]

Inoue, S. and T. Aida, Cyclic Ethers, Chap. 4 in Ring-Opening Polymerization, Vol. 1, K. I. Ivin and... [Pg.610]

The ring-opening polymerization of cyclic ethers having 3-, 4-, and 5-membered rings (e.g., epoxides, oxetanes, THF) yields polymeric ethers. Six-membered rings (1,4-dioxane) are not capable of polymerization. [Pg.206]

Ring opening polymerization of cyclic monomers to yield thermoplastic polymers has been studied by a number of investigators [1-19] over the years. A variety of cyclic monomers ranging in structures from the more commonly encountered olefins, ethers, formals, lactones,... [Pg.41]

Polyethers are prepared by the ring opening polymerization of three, four, five, seven, and higher member cyclic ethers. Polyalkylene oxides from ethylene or propylene oxide and from epichlorohydrin are the most common commercial materials. They seem to be the most reactive alkylene oxides and can be polymerized by cationic, anionic, and coordinated nucleophilic mechanisms. For example, ethylene oxide is polymerized by an alkaline catalyst to generate a living polymer in Figure 1.1. Upon addition of a second alkylene oxide monomer, it is possible to produce a block copolymer (Fig. 1.2). [Pg.43]

Cyclic aryl ether ketones have been prepared from l,2-bis(4-fluorobenzoyl)benzene and bisphenols under pseudo high dilution conditions. These materials undergo ring-opening polymerization in the presence of an anionic catalyst (87). [Pg.333]

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. [Pg.2187]


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Cyclic polymerization

Cyclic ring-opening polymerizations

Ethere cyclic

Ethers cyclic

Ethers, cyclic polymerization

Ring cyclic ethers

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