Ethylene oxide , living anionic polymerization

Key words FT-NIR, kinetics, living polymerization, isobutylene, ethylene oxide, butadiene, anionic polymerization, cationic polymerization... 

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]. 

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 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). 

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... 

Moreover, PFS block co-polymers can be accessed via transition metal-catalyzed ROP of silicon-bridged [l]ferro-cenophanes (Section 12.06.3.3.4) in the presence of a polymer terminated with a reactive Si-H bond. This technique has been used successfully for the synthesis of both diblock and triblock co-polymers. For example, water-soluble PFS-/ -PEO 106 (PEO = poly(ethylene oxide)) has been prepared from monomer 72 and commercially available poly(ethylene glycol) modified at the end group (Scheme 9). In such cases, the polydispersity of the PFS blocks is higher than that obtained from anionic ROP (typically, PDI = 1.4) and the polydispersity of the co-block is determined by that of the original Si-H functionalized material. Nevertheless, block co-polymer syntheses that use the transition metal-catalyzed approach are very convenient, as the stringent purification and experimental requirements for living anionic polymerizations are unnecessary. 

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... 

Recently, Khosravi et al. reported on the change in polymerization mechanism from living anionic polymerization to ROMP. For this purpose, ethylene oxide was polymerized with Ph2CFl and terminated with 4-chloromethylstyrene. The thus-obtained vinyl-terminated poly(ethylene oxide) (PEO) was then reacted with RuCl2(PCy3)2(CHPh) and used for the ROMP of 2,3-difunctional norborn-2-enes to yield the desired poly(PEO-b-NBE) block copolymer (Scheme 19.15) [208]. 

Systematic smdies on the microdomain morphology of linear ABC Mblock terpolymers (hereafter called linear ABC) are limited to several systems. Linear ABC samples were predominantly synthesized by sequential living anionic polymerizations, which limit the kinds of monomers. Thus, polystyrene (PS) and polyisoprene (PI) or polybutadiene (PB) as well as their hydrogenated polymers such as poly(ethylene-a/t-propylene) (PEP) or poly(ethylene-aft-butylene) (PEB) were used as the A and B blocks, while poly(2-vinylpyridine) (P2VP), poly(4-vinylpyridine) (P4VP), poly(methyl methacrylate) (PMMA), poly(tert-buthyl methacrylate) (PtBMA), poly(ethylene oxide) (PEO) or polydimethylsiloxane (PDMS) was used as... 

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. ... 

PS-fr-PBd) star-block copolymers were synthesized by the macromonomer technique in combination with anionic polymerization and ROMP [ 158], following the procedure outlined in Scheme 83. The macromonomers were prepared with two different methods. In the first the living diblock copolymer was reacted with ethylene oxide to reduce the nucleophihcity of the living end followed by termination with 5-carbonyl chloride bicycle (2.2.1) hept-2-ene, while in the second method the functional initiator 5-lithiomethyl bicycle... 

It has been shown recently (10) that such block structures could be tailored precisely by the general method summarized hereabove. It is indeed possible to convert the hydroxyl end-group of a vinyl polymer PA (f.i. polystyrene, or polybutadiene obtained by anionic polymerization terminated with ethylene oxide),into an aluminum alcoholate structure since it is well known that CL polymerizes in a perfectly "living" manner by ring-opening insertion into the Al-0 bond (11), the following reaction sequence provides a direct access to the desired copolymers, with an accurate control of the molecular parameters of the two blocks ... 

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. 

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). 

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. 

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