Polymerization of ethylene oxide

Poly(ethylene oxide) [25322-68-3] (PEO) is a water-soluble, thermoplastic polymer produced by the heterogeneous polymerization of ethylene oxide. The white, free-flowing resins are characterized by the following stmctural formula ... 

Polymerization of ethylene oxide can occur duriag storage, especially at elevated temperatures. Contamination with water, alkahes, acids, amines, metal oxides, or Lewis acids (such as ferric chloride and aluminum chloride) can lead to mnaway polymerization reactions with a potential for failure of the storage vessel. Therefore, prolonged storage at high temperatures or contact with these chemicals must be avoided (9). 

Recent efforts have also been successful in both the polymerization of ethylene oxide and tetrahydrofuran. Both Saegusa et al., and Robinson and Pruckmayr were successful in oligomerizing ethylene oxide under varying conditions. Of somewhat greater... 

A number of polyethylene glycols are also available in molecular weight ranges from commercial suppliers. These are made by initiating the polymerization of ethylene oxide by hydroxide ion. The corresponding monomethyl (or monoalkyl ethers) can be made in a similar fashion by initiating the polymerization with an alcohol. The general reaction is shown below in Eq. (7.2). 

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

Polymerization of ethylene oxide might be initiated by electron transfer process if metallic Na or Li is used as an initiator. On the other hand, initiation by sodium naphthalene involves not electron transfer but addition to naphthalene- ion. 

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. ... 

In a similar manner polyisoprene-polyethylene oxide block copolymers can prepared301. It is surprising that the poly(methyl methacrylate) anion can be successfully used for the polymerization of ethylene oxide without chain transfer302. Graft copolymers are also prepared by successive addition of ethylene oxide to the poly-... 

Cationic polymerization of ethylene oxide is accompanied by depolymerization and oligomerization. It has been reported that ethylene oxide polymerized cation-ically with the living dication of tetrahydrofuran and a surface active material was obtained290. ... 

The free amino group of the amino ester may then react analogously with another molecule of the monomer, etc. The kinetics of the polymerization are in harmony with a mechanism of this sort. The final polypeptide may contain up to 300 or more structural units. While the polymerization of N-carboxyanhydrides is closely analogous to the addition polymerizations of ethylene oxide and of other cyclic substances, definition unfortunately classifies it as a condensation polymerization inasmuch as carbon dioxide is eliminated in the process. 

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. 

In many polymerizations cyclic material is produced by a concurrent backbiting reaction as linear polymer is formed. For example dioxan Is formed In the cationic polymerization of ethylene oxide to polyoxyethylene, and polyoxyethylene can be degraded to... 

The above considerations stimulated investigations of the polymerization of model systems, namely ethylene oxide in the presence of dialkyldichlorostannanes30). R2SnCl2 has been found to be a very active catalyst for the polymerization of ethylene oxide, the polymerization rate increasing considerably with the length of the alkyl substituent at the tin atom. 

PS-b-PEO) , n = 3, 4 star-block copolymers were synthesized by ATRP and anionic polymerization techniques [149]. Three- or four-arm PS stars were prepared using tri- or tetrafunctional benzylbromide initiators in the presence of CuBr/bipy. The polymerization was conducted in bulk at 110 °C. The end bromine groups were reacted with ethanolamine in order to generate the PS stars with hydroxyl end groups. These functions were then activated by DPMK to promote the polymerization of ethylene oxide and afford the desired well-defined products (Scheme 73). 

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...

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-... 

An existing polymer with an appropriate end group can be reacted with an alkoxyamine for instance, alkoxide polymerization of ethylene oxide yields a hydroxyl-terminated polymer that undergoes substitution (in the presence of sodium hydride) with a halogen-containing alkoxyamine. 

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... 

The anionic polymerization of epoxides such as ethylene and propylene oxides can be initiated by metal hydroxides, alkoxides, oxides, and amides as well as metal alkyls and aryls, including radical-anion species such as sodium naphthalene [Boileau, 1989 Dreyfuss and Drefyfuss, 1976 Inoue and Aida, 1984 Ishii and Sakai, 1969]. Thus the polymerization of ethylene oxide by M+A involves initiation... 

Polymers with extremely high molecular weights result from the polymerization of ethylene oxide initiated by the carbonates of the alkaline earth metals, e.g., strontium carbonate, which must, however, be very pure. Poly(ethylene oxides) having molecular weights up to about 600 are viscous liquids above that they are wax-like or solid, crystalline products that are readily soluble not only... 

The polymerization of ethylene oxide (epoxyethane, EO) with 17 also proceeded by irradiation with visible light. For example, the polymerization with the mole ratio [EO]o/[17]o of 190 in benzene at room temperature, where the monomer conversion after 205 min was very low (<2%, determined by H NMR) in the dark, proceeded to 97% conversion in only 80 min under irradiation. The Mn of the polymer, as estimated from the GPC chromatogram, was 8700, which is in excellent agreement with the expected value of 8100 provided that the numbers of the molecules of the produced polymer and 17 (X=SPr) are equal [81]. The Mw/Mn of the polymer (1.05) was close to unity, indicating the livingness of the visible Hght induced polymerization of EO initiated with (NMTPP)ZnSPr (17). 

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). 

Figure 1.3 Cationic polymerization of ethylene oxide in the presence of an alcohol...

Figure 1.4 Polymerization of ethylene oxide by nucleophilic mechanism...

These and related heterocyclic monomers are usually highly polar and strongly nucleophilic conpounds. During polymerization chains containing heteroatoms are formed and they can, as well as monomers themselves, interact with components of ionic growing species. The interaction of the macroion-pairs with the elements of the chains has well been documented for the polymerization of ethylene oxide [Z]. 

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

Diethyizinc is not an active catalyst for polymerization of ethylene oxide and propylene oxide, but gives a high molecular weight polymer from styrene oxide (78) and a copolymer from styrene oxide and propylene oxide (79). This behavior is interpreted by assuming that styrene oxide easily reacts with diethyizinc to give a catalytically active species Zn[OCH2CH PhEt]2 (79,80). 

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