Ethylene oxide polymers, molecular weight

Heterogeneous Catalytic Polymerization. The preparation of polymers of ethylene oxide with molecular weights greater than 100,000 was first reported in 1933. The polymer was produced by placing ethylene oxide in contact with an alkaline-earth oxide for extended periods (61). In the 1950s, the low yield and low polymerization rates of the eady work were improved upon by the use of alkaline-earth carbonates as the catalysts (62). 

Polyethyleneoxide-co-polypropyleneoxides, dispersants, S 710t Poly(ethylene oxide) film, physical properties of, 10 68It Poly(ethylene oxide) floe, 11 638 Poly(ethylene oxide)-poly(ethylene terephthalate) copolymers, bioresorbable polymers, 3 738 Poly(ethylene oxide) resins, molecular weight of, 10 684-685 Polyethylene oxides, dispersants, S 706t, 710t... 

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... 

A comparison of the degree of crystallinity obtained by gas chromatography for poly(ethylene oxide) of molecular weight 40 000 with those determined by IE spectroscopy and X-ray diffraction yields [183] 74% for the first method when the polymer film thickness was 6.5 X10" cm, 75.9% for the second (film thickness 5.1X10 cm) and 79.1% for the last method. The differences were ascribed to the incomplete development of crystallinity in the films used in gas chromatography and IE s ctroscopy, these films being thinner than the diameter of the spherulites. 

Poly(ethylene oxide)s [25372-68-3] are made by condensation of ethylene oxide with a basic catalyst. In order to achieve a very high molecular weight, water and other compounds that can act as chain terminators must be rigorously excluded. Polymers up to a molecular weight of 8 million are available commercially in the form of dry powders (27). These must be dissolved carefliUy using similar techniques to those used for dry polyacrylamides. Poly(ethylene oxide)s precipitate from water solutions just below the boiling point (see Polyethers, ethylene oxide polymers). 

Fig. 3. Solution viscosity vs concentration for ethylene oxide polymers (10). The molecular weight of the polymer is indicated on each curve. The dependence of the intrinsic viscosity [Tj] on molecular weight M for these polymers can be expressed by the Mark-Houwink relationship ...

In 1958 the Union Carbide Corporation introduced high molecular weight, highly crystalline ethylene oxide polymers under the trade name Polyox. Although similar in appearance to polyethylene they are miscible with water in all proportions at room temperature. 

Table 19.5 Some properties of a medium-high molecular weight ethylene oxide polymer ...

Poly(ethylene oxide) (PEO), 10 665, 673-674 13 540, 542-543, 731. See also Ethylene oxide polymers association reactions of, 10 682 behavior in solution, 10 685 commercial block copolymers, 7 648t crystallinity of, 10 690 as a flocculating agent, 11 630-631 low molecular weight, 14 259 oxidation of, 10 682 in paper manufacture, IS 117 preparation of, 20 462 Polyethylene oxide chains, in cationic surfactants, 24 147... 

Fig. 3. Solution viscosity vs concentration for ethylene oxide polymers (10). The molecular weight of the polymer is indicated on each curve.

Di Colo, G., Burgalassi, S., Chetoni, R, Fiaschi, M. P, Zambito, Y., and Saettone, M. F (2001), Relevance of polymer molecular weight to the in vitro/in vivo performances of ocular inserts based on poly(ethylene oxide), Int. J. Pharm., 220(1-2), 169-177. 

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