Polyethylene oxide molecules

We can now estimate the theoretical gel point in this system the mean molecular mass of this mixture is calculated to be j 1000+j 465 = 786 (g I mol) for the equimolar case (k = 1). Considering the dilution effect (33 w / w %) by dioxane, it follows that y 2All mol. The polyethylene oxide molecule of interest is composed of 70 skeletal bonds on average. Due to this long backbone along with the dense solution, it can be approximated that the structural unit follows Gaussian statistics. With the Flory characteristic constant [6], C = (r2)/nf2=4,for polyethylene oxide in the 0 regime, one has... 

In the presence of polyethylene oxide MW 300,000 at a concentration of 0.025 g liter , variations in pH and ionic strength have no effect on elution volumes and a single calibration curve is obtained as shown in Figure 4 and Table II. This behavior presumably also results from modification of the glass surface by the polyethylene oxide surfactant, but in this case charge effects appear to be completely suppressed and the effective pore diameter and volume reduced. Such an interpretation is also in accord with the fact that the elution voliomes are lower with polyethylene oxide than with Tergitol, since Tergitol is a much smaller molecule than the polyethylene oxide. 

Research in this field is ongoing aiming to understand the mechanism of action of kinetic inhibitors. Lee and Englezos (2005) showed that inclusion of polyethylene oxide (PEO) to a kinetic inhibitor solution was found to enhance by an order of magnitude the performance of the hydrate inhibitor. Binding of inhibitor molecules to the surface of hydrate crystals was considered to be the key aspect of the mechanism of kinetic inhibition (Anderson et al.,... 

If a mechanical degradation of a solution of two polymers is carried out by high speed stirring, the formation of a block copolymer is not probable as the scission of polymer molecules at low concentration is not caused mainly by intermolecular interaction, such as by collision of molecules and through entanglements, but by displacements due to hydrodynamic forces in velocity gradients. Nakamo and Minoura (98) did obtain reaction by stirring a benzene solution of polyethylene oxide and poly(methyl methacrylate). 

Curve 3 in Figure 7.14 applies primarily to amphipathic species. Most long-chain amphipathic molecules are insoluble unless the hydrophobic alkyl part of the molecule is offset by an ionic head or some other suitably polar head such as a polyethylene oxide chain, — (CH2CH20)n—. Like their insoluble counterparts, these substances form an oriented monolayer even at low concentrations. Figure 7.15 shows some actual experimental plots of type 3 for the ether that consists of a dodecyl chain and a hexaethylene oxide chain (n — 6) in the general formula just given. Example 7.4 illustrates the application of the Gibbs equation to these data. 

It is, of course, possible to prepare a molecule that has both polar and nonpolar characteristics. This is the basis of surfactant chemistry. Typically, a nonpolar molecule is modified by sulfonation. The well-known Pluronic family of surfactants is based on block polymerization of polypropylene oxide (the hydrophobe) and polyethylene oxide (the hydrophUe). It is conceptually possible to build a polyurethane 2005 by CRC Press LLC... 

The gels can incorporate even polymers such as, for example, water-soluble polyethylene oxide (PEO), polyvinylpyrrolidone (PVP), and polypropyl-eneglycol (PPG). For the PE0/V205 system the interlayer broadening achieved 13.2 A, which corresponds to more probable placement of the polymer molecules along the layers [1373] (Fig. 11.1 b). 

Example 12.1. The CMC of C12E7 is 0.083 mM at room temperature. By SANS and dynamic light scattering the mean hydrocarbon core radius was found to be 1.70 nm at a surfactant concentration of 2 mM [532], The mean aggregation number is 64. If we divide the total surface area of the core by the number of surfactants, we get the area per molecule at the core radius. It is 47r (1.7 nm)2 /64 = 0.57 nm2. The cross-sectional area of polyethylene oxide is below 0.2 nm2. So, more than half the core area is exposed to aqueous or at least to a polar medium. 

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