Ethylene oxide , ring-opening polymerization

Obtained by the ethylene oxide ring-opening polymerization using Friedel-Crafts catalysts such as boron trifluoride, tin tetrachloride or zinc chloride, or acid or alkali catalysts. 

Ethylene oxide Ring-opening polymerization Molecular weights 200 to 600— surfactants, humectants, lubricants Molecular weights >600 pharmaceutical and cosmetic bases, lubricants, mold release agents Molecular weights 10 to 5 X10 — water-soluble packaging films and capsules... 

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. 

By using a combination of RAFT and ring opening polymerization (ROP), (polyethylene oxide) methyl ether)(polystyrene)(poly(L-lactide) 3-miktoarm star terpolymers have been successfully synthesized [182]. The synthetic approach involved the reaction of the cw-functionalized - OH group of the poly(ethylene oxide) methyl ether with maleic anhydride under conditions where only one hydroxyl group can be esterified (MPEO). The double bond... 

Fig. 7 Synthesis of heterobifunctional PEG. (a) Nagasaki et al. developed a method for the polymerization of EO using an initiator containing defined functionalities [16, 17]. (b) Akiyama et al. further developed a synthetic route to prepare a series of heterobifunctional PEGs [18-21]. After the ring-opening polymerization of ethylene oxide, a second functional group was introduced at the co-end of PEG...

Five-coordinate aluminum alkyls are useful as oxirane-polymerization catalysts. Controlled polymerization of lactones102 and lactides103 has been achieved with Schiff base aluminum alkyl complexes. Ketiminate-based five-coordinate aluminum alkyl (OCMeCHCMeNAr)AlEt2 were found to be active catalyst for the ring-opening polymerization of -caprolactone.88 Salen aluminum alkyls have also been found to be active catalysts for the preparation of ethylene carbonate from sc C02 and ethylene oxide.1 4 Their catalytic activity is markedly enhanced in the presence of a Lewis base or a quaternary salt. 

A similar ring-opening polymerization (ROP) with ethylene oxide forming poly(ethyl-ene oxide) forms a noncarbon backbone via a chainwise kinetic process ... 

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... 

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). 

Kinetics of anionic ring-opening polymerization has hitherto been quantitatively studied and gave for two monomers, namely ethylene oxide [IS,12] and propylene sulfide [8.20]. Studies on these systems revealed that the living conditions can be achieved, facilitating quantitative determination of rateconstants of propagation on various kinds of ionic growing species. 

The PEO salt complexes are generally prepared by direct interaction in solution for soluble systems or by immersion method, soaking the network cross-linked PEO in the appropriate salt solution [52-57]. Besides PEO, poly(propylene)oxide, poly(ethylene)suceinate, poly(epichlorohydrin), and polyethylene imine) have also been explored as base polymers for solid electrolytes [58]. Polyethylene imine) (PEI) is prepared by the ring-opening polymerization of 2-methyloxazoline. Solid solutions of PEI and Nal are obtained by dissolving both in acetonitrile (80 °C) followed by cooling to room temperature and solvent evaporation in vacuo. Polyethyleneimine-NaCF3S03 complexes have also been explored [59],... 

The ring-opening polymerization of cyclic monomers can be performed by ionic chain polymerization, as is the case of epoxy monomers. Anionic polymerization of ethylene oxide propylene oxide, and caprolactone can be initiated by alkoxides ... 

The exterior of carbosilane dendrimers can also serve as initiator sites for polymerization, in which case the dendrimers serve as cores for star polymers. Vasilenko and coworkers95 synthesized a multilithiated carbosilane dendrimer which they then used as an initiator for the ring-opening polymerization of hexamethylcyclotrisiloxane to yield star polymers of narrow weight distribution (Scheme 7). The researchers later extended this work to polymerize styrene, isoprene and ethylene oxide96,97. Star poly(ethylene oxides) were also prepared using hydroxy-terminated carbosilane dendrimers as the core98,99. 

One polymer that isoften used in these products is poly ethylene oxide) (PEO), a polymer most often prepared by the ring-opening polymerization of ethylene oxide (see Table 5-3). Alternatively, it is sometimes prepared by a step-growth polymerization of ethylene glycol, in which case it is called polyethylene glycol) (PEG). PEO/PEG is a water-soluble polymer that can be synthesized to a molar mass in the millions. 

Other important examples of ring-opening polymerizations are the synthesis of polyethylene oxide and the block copolymer of ethylene oxide and propylene oxide. Polyethylene oxide, also known as polyethylene glycol (PEG), is commonly produced by anionic polymerization and has a low molecular weight of less than 20,000. 

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