Anionic polymerization of ethylene oxide

Polyethylene glycol), or Carbowax, is made by anionic polymerization of ethylene oxide using NaOH as catalyst. Propose a mechanism. 

Anionic polymerization of ethylene oxide by living carbanions of polystyrene was first carried out by Szwarc295. A limited number of methods have been reported in the preparation of A-B and A-B-A copolymers in which B was polystyrene and A was poly(oxyethylene)296-298. The actual procedure was to allow ethylene oxide to polymerize in a vacuum system at 70 °C with the polystyrene anion initiated with cumyl potassium in THF299. The yields of pure block copolymers are usually limited to about 80% because homopolymers are formed300. ... 

Depending on polymerization conditions, PEG termini may consist of hydroxyl groups or may be selectively functionalized. Commercially available PEG is produced through anionic polymerization of ethylene oxide to yield a polyether struc-... 

Propagation Constants of Ion Pairs and Free Ions for the Anionic Polymerization of Ethylene Oxide In THF at 20eC... 

Polymerizations proceeding without any termination were known for a long time, e. g. it was realized that the anionic polymerization of ethylene oxide (23) might exemplify such a situation. The subject has been recently brought into focus by this writer (24,25) who proposed also the name living polymers for those polymeric species that did not lose their ability to grow further. The introduction of this term is justified by the existence of an older term — dead polymers which denotes those polymeric molecules that did lose their ability to grow, i.e. polymeric molecules that are terminated. 

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 ... 

Introduced as a chain-end group, the BBN group was converted to an alkoxide group, that is, -0 K+, an efficient initiator for anionic polymerization for ethylene oxide. The ring opening living anionic polymerizations of ethylene oxide were carried out with potassium alkoxide polyolefins to prepare polycthylcnc-block-poly(cthylcnc oxide) (PE-fc-PEO), poly(ethylene-co-styrene)-foZock-poly(ethylene oxide), and poly(ethylene-co-octene)-Mock-poly(ethylene oxide) (EOR-fo-PEO) [37]. 

Rod—coil molecules containing structurally perfect conjugated rods were synthesized by using a-(phen-yl)-ft -(hydroxymethyl phenyl)-poly(fluoren-2,7-ylene) as macroinitiator (Scheme 8).98 Anionic polymerization of ethylene oxide by using the macroinitiator produced a corresponding rod—coil block copolymer (22). The absorption and emission measurements of... 

B-90 and B-91, respectively.390 Another route coupled with cationic ring-opening polymerizations is accomplished for polymer B-92 with the use of a hydroxyl-functionalized initiator with a C—Br terminal, where the OH group initiates the cationic polymerizations of 1,3-dioxepane in the presence of triflic acid.329 Polyethylene oxide)-based block copolymers B-93 are obtained by living anionic polymerization of ethylene oxide and the subsequent transformation of the hydroxyl terminal into a reactive C—Br terminal with 2-bromopropionyl bromide, followed by the copper-catalyzed radical polymerization of styrene.391... 

QUIRK AND SEUNG Anionic Polymerization of Ethylene Oxide... 

Ethylene Oxide Polymerization. The apparent inability of lithium bases to effect the anionic polymerization of ethylene oxide and Its homologues Is unique among the alkali metals. At least part of the unreactlvlty of lithium alkoxldes can be ascribed to their strong association In solution as shown In Table 1(18). However, It can be seen that the corresponding sodium and potassium alkoxldes are also highly associated In solution and yet they are active Initiators for the polymerization of ethylene oxide. 

In a series of papers43 4S), the kinetics of anionic polymerization of ethylene oxide in conjunction with different catalysts were studied. These studies expand our understanding of the mechanism of living polymerization systems and provide new information on the processes of active center association. Herein, primarily, lies the specific nature of the heteroatomic systems, as compared with the vinyl monomers studied earlier 9 ... 

Vinylmagnesiumchloride was also used to produce PMMA macromonomers [115]. Using similar techniques, several macromonomers have been prepared by the anionic polymerization of ethylene oxide, butadiene, isoprene, 2-vinylpyri-dine, a-methylstyrene, vinylpyrrolidone etc. Table 2 summarizes the data reported in the literature concerning the synthesis of graft copolymers with anionically prepared macromonomers. 

The linear-dendritic copolymer [G-3]-PE013k has a linear poly-(oxyethylene) block with molecular weight of 13,000 Da (PE013k) and was formed via living anionic polymerization of ethylene oxide initiated by a... 

Ethylene Oxide The anionic polymerization of ethylene oxide is complicated by the association phenomenon and the participation of ion-pair and free ion intermediates in the propagation reactions [129, 130]. Simple lithium alkoxides are strongly associated into hexamers and tetramers even in polar media such as THE and pyridine [130]. As a consequence, lithium alkoxides are unreactive as initiators for the anionic polymerization of oxiranes. Association effects can be minimized by effecting polymerizations in alcohol media or in dipolar aprotic solvents. 

Anionic polymerizations of ethylene oxide were originally observed as early as the end of the last century. A step-growth mechanism for these polymerizations was proposed later.This mechanism is now well established. The conversion increases linearly with time and the molecular weight also increases with conversion. Reactions with bases like sodium or potassium hydroxides or alkoxides yield only low molecular weight polymers. The initiation, an Sa 2 displacement, results in the formation of an alkoxide ion ... 

Triblock PEO-PDMS-PEO copolymers have been obtained by anionic polymerization of ethylene oxide using a PDMS diol as transfer agent. These copolymers have been fully characterized by NMR and Maldi-Tof mass spectrometry. As expected, the solubility depends on the PEO/PDMS ratio [42]. 

PCL with the TEMPO 2,2,6,6-tetrameihYlpiperidinoxyl) moiety behaved as a polymeric counter-radical for the polymerization of styrene, resulting in the quantitative formation of PCL-fo-PSt. The radical polymerization was found to proceed in accordance with a living mechanism, without undesirable side reactions. The thermal analysis of the block copolymer indicated that the components of PCL and PSt were completely immiscible and microphase-separated. Incorporation of the TEMPO moiety into PEO chain-ends in the radical form was also achieved [53]. In this case, TEMPO-Na was used as an initiator in a hving anionic polymerization of ethylene oxide (Scheme 11.10), under conditions such that the stable nitroxyl radical at the end of the PEO chain could not be destroyed. 

Bayer described grafting of PEG onto PS resin, by direct anionic polymerization of ethylene oxide onto poly(styryl-methyltetraethylene glycol ether) (68). 

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