Living anionic polymerization of ethylene oxide

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]. 

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... 

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... 

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. ... 

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. 

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 ... 

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. 

In Section 3.02.11, steady-state living polymerization was discussed. Initiation has been assumed to be fast as compared with propagation. This is then a class of polymerizations where the number of propagating chains remains invariant throughout the course of reaction. Such a situation exists, for example, in anionic polymerization of ethylene oxide, described by Floty, who has shown that such a process leads to the Poisson distribution. ... 

Many homogeneous catalytic processes, in particular of anionic nature, are known, in which the polymerization takes place by stepwise addition (polymerization of ethylene oxide (34) of ethylene at low pressure and temperature with ALfia (7, 35), of styrene by Szwarc catalysts (36), for which the growth of the macromolecule can last for a very long time). This led some researchers to talk of a life of macromolecules and of living molecules (37). 

In contrast to many other functionalization reactions, termination of living anionic polymers with ethylene oxide, (Eq. (79)) is relatively free of side reactions other than polymerization. For example,... 

The synthesis and purification of polystyrene methacryloyl macromonomers (PS-MA) in the molecular weight range Mn= 1000-2000 g mol 1 by living anionic polymerization of styrene (S), termination with ethylene oxide (EO), and subsequent reaction with methacrylic chloride has already been described in detail elsewhere [180] (see also Scheme 16). In this context it has to be emphasized that the hydroxyethyl-terminated PS-MA macromonomer precursor (PS-OH) as obtained after purification of the crude PS-OH by silica column chromatography (cyclohexane/dichloromethane 1/1 v/v) and as charged in the PS-MA synthesis still contains up to about 15 wt-% of non-functionalized polystyrene (PS-H). This PS-H impurity of the PS-MA macromonomer does not interfere with the PS-MA synthesis and the subsequent TBA/PS-MA copolymerization and is easily and conveniently removed from the resulting PTBA-g-PS graft copolymer (see below). 

Onium ions will be very short-lived in the polymerization of D3, even when water is not added, because the strained onium ions rapidly collapse with anions. There is an analogy with the polymerization of ethylene oxide and THF with TfOe. In... 

Recently the synthesis of poly(IB-b-ethylene oxide) diblock copolymer has been reported [245]. In the first step, LfO-functional PIB was prepared by hydrobora-tion/oxidation of allyl functional PIB, obtained in the reaction of living PIB and ATMS. The ring-opening polymerization of ethylene oxide was initiated by the PIB alkoxide anion in conjunction with the bulky phospazene t-BuP4. 

The range of monomers that can be incorporated into block copolymers by the living anionic route includes not only the carbon-carbon double-bond monomers susceptible to anionic polymerization but also certain cyclic monomers, such as ethylene oxide, propylene sulfide, lactams, lactones, and cyclic siloxanes (Chap. 7). Thus one can synthesize block copolymers involving each of the two types of monomers. Some of these combinations require an appropriate adjustment of the propagating center prior to the addition of the cyclic monomer. For example, carbanions from monomers such as styrene or methyl methacrylate are not sufficiently nucleophilic to polymerize lactones. The block copolymer with a lactone can be synthesized if one adds a small amount of ethylene oxide to the living polystyryl system to convert propagating centers to alkoxide ions prior to adding the lactone monomer. 

Norbornenyl-ended macromonomers from poly(ethylene oxide) (PEO), 15, as well as from PEO-b-PSt or PSt-b-PEO block copolymers, 16a, 16b, have been prepared by the initiation or termination method of living anionic polymerization [22, 23]. The ROMP of 16 afforded various types of controlled, core-shell... 

The first block (polybutadiene or polystyrene) is prepared by anionic polymerization, under high vacuum, in THF dilute solution (less than 5%), at low temperature (—70 °C) with cumylpotassium as initiator. Then, the living polymer is transformated into a hydroxylated polymer (PV—OH) by addition of ethylene oxide under vacuum, or into a carboxylated polymer (PV-COOH) by addition of carbon dioxide under vacuum. 

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