Polyethylene oxide chains

Another subclass of substituted amides that is of great commercial value is the ethoxylated amides. They can be synthesized from alkanolamides by chain extending with ethylene or propylene oxide or by ethoxylation directly from the primary amide (46—48). It was originally beheved that the stepwise addition of ethylene oxide (EO) would produce the monoethano1 amide and then the diethanolamide when sufficient ethylene oxide was added (49), but it has been discovered that only one hydrogen of the amide is substituted with ethylene oxide (50—53). As is typical of most ethylene oxide adducts, a wide distribution of polyethylene oxide chain length is seen as more EO is added. A catalyst is necessary to add ethylene oxide or propylene oxide to a primary or an ethoxylated amide or to ethoxylate a diethoxy alkanolamide synthesized from diethanolamine (54). 

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... 

Figure 2.8 Part of a polyethylene oxide chain using wire frame and space-filling models.

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. 

Sometimes branched units are synthesized and further condensed to graft copolymer e.g. dimethylterephthalate carrying in the aromatic nucleus polyethylene oxide chains is transesterified with ethylene glycol and polycondensed. 

Recently, a new class of inhibitors (nonionic polymer surfactants) was identified as promising agents for drug formulations. These compounds are two- or three-block copolymers arranged in a linear ABA or AB structure. The A block is a hydrophilic polyethylene oxide) chain. The B block can be a hydrophobic lipid (in copolymers BRIJs, MYRJs, Tritons, Tweens, and Chremophor) or a poly(propylene oxide) chain (in copolymers Pluronics [BASF Corp., N.J., USA] and CRL-1606). Pluronic block copolymers with various numbers of hydrophilic EO (,n) and hydrophobic PO (in) units are characterized by distinct hydrophilic-lipophilic balance (HLB). Due to their amphiphilic character these copolymers display surfactant properties including ability to interact with hydrophobic surfaces and biological membranes. In aqueous solutions with concentrations above the CMC, these copolymers self-assemble into micelles. 

Fig. 4 The number of nitrogen atoms, which equals the number of sugar units, per cm2 (filled squares) and the number of polyethylene oxide) chains per cm2 (unfilled circles)...

Fig. 3. Basic reaction of glycidyloxypropyl-trimethoxysilane (GPTS) to form polyethylene oxide chains...

Surfactants for urethane and related polymer foams are usually silicone-surfactants. These surfactants generally are copolymers of poly(dimethylsiloxane) [-Si(CH3)2-0-] , oxyalkylene chains, e.g., polyethylene oxide chain (EO) , and polypropyene oxide chains, (PO) . The copolymers can be linear, branched or pendant types. The surfactants have different functions, i.e., emulsifying, foam stabilizing, and cell-size control. 

The calculation cannot be carried out in an accurate way because, as mentioned before, the mixing rule between anionic and non-ionic surfactants is not actually linear due to a shielding of the ionic group by the polyethylene oxide chain. However, the use of a linear approximation often leads to a fairly good estimate in some cases such as a mixture of alkylbenzene sulphonates and ethoxylated nonylphenols to be considered as an example next [61]. 

It was observed experimentally that if the EO addition rate is high (in fact a high ethoxylation pressure), cloudy polyols and low primary hydroxyl content are formed [51]. The explanation of this behaviour is that if the rate of EO addition is too high, the equilibrium of alcohol - alcoholate does not have enough time to get established and the polyethylene oxide chains grow on a limited number of hydroxyl groups. As an immediate... 

Ini 987,Xie and Xia reported the synthesis of A2B2 and A2B miktoarm stars, where A is PS and B is PEO [228]. Their method involves the reaction of living polystyrene chains with SiCl4 in a molar ratio 2 1. This reaction leads to the formation of a two arm star with the remaining Si-Cl bonds available for reaction with the living polyethylene oxide chains in order to produce the (PS)2(PEO)2 stars (Scheme 74). 

Specific complexation of cations by polyethylene oxide chains (PEGs 1), macrocyclic (crown ethers 2-4) or macrobicyclic (cryptands 5) polyethers facilitates salt dissolution in low-polarity solvents, at the same time providing nonsolvated highly reactive anions by increasing ion-pair dissociation (Chart 1) [37],... 

Monofunctional hydroxyl terminated polyethylene oxide chains with degree of polymerization from 5 to 20 are reacted with pMDI, or simply with MDI, to provide surface active agents. The resulting surface active agent is then mixed with pMDI to provide a resin which is dispersible in water, resulting in an oil-in-water emulsion [51]. Such emulsions are stable for brief periods, 1 to 2 hours, before the water reaetion eauses gelation. Emulsifiable pMDI could be used where dispersion in water offers some benefit. For example, neat emulsifiable pMDI could be added directly to the blow line for medium density fiberboard production. Water emulsified pMDI has been used for improving resin distribution in particleboard or OSB manufacture however, this is not common industrial practice. 

The first three effects are readily explained by the change in R numerator and denominator. As the surfactant lipophilic tail" gets longer, the imeraciion with the oil phase Aco is increased. In a similar way, a longer polyethylene oxide chain (hydrophilic group) of a nonionic surfactant results in an increase of the interaction with water Ac . 

HLB -= weight of polyethylene oxide chain 5 total molecular weight... 

Y. Mori and S. Nagaoka. A new antithrombogenic material with long polyethylene oxide chains. Trans. Am. Soc. Artif. Intern. Organs 28 459-463 (1982). 

The WLF formula shows that the ionic conductivity of the polymer electrolyte is shown in the temperature range higher than Tg. Ionic conductivity decreases rapidly if its temperature goes below that of Tg. The EO unit is recognized as the most excellent structure from the ionic dissociation viewpoint. The ion is transported coupled with the oxyethylene chain motion in amorphous polymer domain. However, oxyethylene structure easily becomes crystalline. Therefore, in order to accelerate the quick molecular motion of the polymer chain and quick ion diffusion, it is important to lower the crystallization of polymer matrixes. The methods for inhibiting the crystallization of the polymer are, for example, to introduce the polyethylene oxide chain into the low Tg polymer such as polysiloxane and phosp-hazene, or to introduce the asymmetric units such as ethylene oxide/propylene oxide (EO/PO) into polymer main chain. 

Solubility of Nonionic Surfactants. Nonionic surfactants owe their solubility in water to hydration of the polyethylene oxide chains. The solubility of these surfactants in water increases as the length of the... 

Table 3 lists several of the hydrophobic acrylate-based polymers currently being investigated. This list can be broken down into two categories, separated by the horizontal line through the table. Hydrophobic acrylates in the upper portion (page 244) have their hydrophobic entity in close proximity to the acrylate backbone. Those in the lower (page 245) portion of the table have their hydrophobic entity separated from the acrylate backbone by a polyether (typically polyethylene oxide) chain. While the presence of the polyether chain is not required for an associative mechanism to operate, it has been demonstrated that its presence can influence viscosity (84). In particular, nonionic surfactants that themselves contain polyether chains seem to have a particular attraction to the polyether chains of the associative thickener. 

The polyethylene oxide chains attached to the cellulose backbone in HEC lack the hydrophobic influences of the pendent methyl groups (—CH3) present in the methyl (MC, HPMC) ethers, or from the methyl groups of propylene oxide (HPC, HPMC) found in the other cellulose ethers mentioned. As a result, HEC is more tolerant to extremes of pH, salts, and surfactants than the other cellulose ethers. Hydration of HEC can be troublesome because the polysaccharide lacks a cp this inverse solubility allows the other cellulose ethers to disperse at high temperatures and then rapidly hydrate as the temperature is lowered through the cp. Care must be taken to assure that small, only partially hydrated spheres, or flsheyes, do not form while HEC solutions are dissolving. 

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