RING-OPENING POLYMERIZATION OF EPOXIDES

EO = ethylene oxide, PO = propylene oxide, Et-EO = 1,2-epoxybutane, Bu-EO =1 butylethylene oxide, BO = 2,3-epoxybutane, ECH = epichlorohydride, CHO = cyclohexene oxide 

Higher molecular weight materials are typically prepared using coordination catalysts, such as the calcium amide-alkoxide system developed by Union Carbide,932 and double metal cyanide initiators, e.g., [Zn(Fe(CN)6)].933 The nature of the active sites in these catalysts is not well understood and only a few studies have been published outside the patent literature.810,934,935 

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Curing of epoxy resins can also be achieved by ring-opening polymerization of epoxide groups using either Lewis acids (including those generated photochemically) or Lewis bases (Sec. 7-2). 

Ring-Opening Polymerization of Epoxide Initiated with... 

Living and Immortal Ring-Opening Polymerizations of Epoxide... 

Ring-Opening Polymerization of Epoxide Initiated with Aluminum Porphyrin in the Presence of an Organoaluminum Compound [60]... 

Ring-Opening Polymerization of Epoxide with Various Aluminum Complexes as Initiators in the Presence of a Lewis Acid... 

Another commercial application of organoaluminum compounds is as catalysts for the ring-opening polymerization of epoxides to form homopolymers of epichlorohydrin (ECH) and copolymers and terpolymers of ECH, ethylene oxide, propylene oxide, and allyl glycidyl ether.The resulting... 

Of intermediate utility between these two extremes for anionic polymerization is alkoxide ion, which has adequate base strength for initiation of the ring-opening polymerization of epoxides (Eqs. 22.24-22.26). 

Photoinitiated cationic polymerization has been the subject of numerous reviews. Cationic polymerization initiated by photolysis of diaryliodonium and triarylsulfonium salts was reviewed by Crivello [25] in 1984. The same author also reviewed cationic photopolymerization, including mechanisms, in 1984 [115]. Lohse et al. [116], reviewed the use of aryldiazonium, diphenyliodonium, and triarylsufonium salts as well as iron arene complexes as photoinitiators for cationic ring opening polymerization of epoxides. Yagci and Schnabel [117] reviewed mechanistic studies of the photoinitiation of cationic polymerization by diaryliodonium and triarylsulfonium salts in 1988. Use of diaryliodonium and sulfonium salts as the photoinitiators of cationic polymerization and depolymerization was again reviewed by Crivello [118] in 1989 and by Timpe [10b] in 1990. 

The most important limitation related to commercial applications is relatively low reactivity of epoxide-based resins, commonly used in coatings, compared to acrylate based systems. Therefore, most works have been effort to accelerate ring-opening polymerization of epoxides. There are four different strategies to speed up the polymerization ... 

Three-membered cyclic ethers (see Table 10.1) are known as epoxides, the simplest epoxides being ethylene oxide and propylene oxide. Their polymerization is a subject of considerable technological importance. The ring-opening polymerization of epoxides can be initiated by both anionic and cationic methods. 

Photoinitiated Ring-Opening Polymerization of Epoxidized Polyisoprene... 

Different initiation techniques have been investigated in polymerizations induced by iodonium salts, such as visible laser irradiation [32], dual photo- and thermally initiated cationic polymerization [23, 26] and a two-photon photopolymerization initiation system [33,34]. For example, dual photo- and thermal-initiation systems based on selective inhibition of the photoinifiated cationic ring-opening polymerization of epoxides by dialkyl sulfides have been developed [26]. Such a dual system, iodonium salt/dialkyl sulfide, in the... 

Ic, brings about ring-opening polymerization of epoxides (11, Table 1) to give polyethers with a narrow molecular weight di.stribution (MWD). 

Polyether synthesis From activated or metal-free anionic ring-opening polymerization of epoxides to functionahzation 13PPS845. 

Sigwalt, P. Stereoelection and stereoselection in the ring-opening polymerization of epoxides and episulfides. Pure Appl. Chem. 1976, 48, 257-266. 

Compounds such as [Al(R)(OC6H3Bu2-2,6)2] will carry out the polymerization of methyl and ethyl methacrylate when activated with t-BuLi. The nature of the alkyl group was found to affect the tacticity of the polymer. The tetraphenylporphinato aluminium phenoxide has been shown to be active for the ring opening polymerization of epoxides and lactones. The reaction is accelerated by the presence of reagents such as MAD. An adduct [Al(OC6H2Bu2-2,6-Me-4)Me2(methyhnethacrylate)] relevant to this reactivity has been isolated and structurally characterized. ... 

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