Nonpolar oils

As a result of many painstaking investigations, the soils on apparel encountered in laundering have been shown to be complex mixtures containing both oily and finely divided soHd material (1,2). The oily material consists largely of fatty acids and polar fatty material but a considerable proportion of neutral nonpolar oil is also present. The soHd components vary widely with the locale in which samples are taken, and resemble local street dust in composition. 

Thermodynamics of adsorption at liquid interfaces has been well established [22-24]. Of particular interest in view of biochemical and pharmaceutical applications is the adsorption of ionic substances, as many of biologically active compounds are ionic under the physiological conditions. For studying the adsorption of ionic components at the liquid-liquid interface, the polarized liquid-liquid interface is advantageous in that the adsorption of ionic components can be examined by strictly controlling the electrical state of the interface, which is in contrast to the adsorption studies at the air-water or nonpolar oil-water interfaces [25]. 

One important advantage of the polarized interface is that one can determine the relative surface excess of an ionic species whose counterions are reversible to a reference electrode. The adsorption properties of an ionic component, e.g., ionic surfactant, can thus be studied independently, i.e., without being disturbed by the presence of counterionic species, unlike the case of ionic surfactant adsorption at nonpolar oil-water and air-water interfaces [25]. The merits of the polarized interface are not available at nonpolarized liquid-liquid interfaces, because of the dependency of the phase-boundary potential on the solution composition. 

Many anionic surfactants are too hydrophilic to be effective in removing nonpolar oils from synthetic fabrics, which requires conditions where hydrophilic... 

Filming inhibitors are characterized by possessing a polar, electron dense head and a nonpolar, oil-soluble tail. Examples of compounds which have these... 

The cleaning power of soaps can be attributed to the polar characteristics of the soap molecule. Long chain hydrocarbons are represented by the R s in Figure 15.16. This end of the molecule is nonpolar and tends to dissolve in nonpolar oils and grease (remember the rule from Chapter 11 that like dissolves like ). The other end of the soap molecule is ionic and dissolves in water. The process of how soap works can be thought of as one end of the soap molecule attracting the grease and oil particles and the other end... 

Oil and water are difficult to mix, as is evident from this oil spill off the coast of Spain in 2002. It s not, however, that oil and water repel each other. Rather, water molecules are so attracted to themselves because of their polarity that they pull themselves together. The nonpolar oil molecules are thus excluded and left to themselves. Being less dense than water, oil floats on the surface, where it poses great danger to birds and other wildlife. 

Polar molecular substances are also soluble in polar water molecules. When a molecular substance such as ethyl alcohol (C2H5OH) dissolves in water (H20), polar ethyl alcohol molecules bond with polar water molecules. In general, likes dissolve likes. Polar solutes will dissolve in polar solvents. In addition, nonpolar solutes dissolve in nonpolar solvents. Nonpolar octane (C8H18) dissolves in nonpolar carbon tetrachloride (CC14). It follows that solutes and solvents of opposite polarity do not form solutions. Nonpolar oil does not dissolve in polar water. (Polar means bearing a charge.)... 

Put a drop of oil and a drop of water on a piece of wax paper. Tilt the wax paper so the drops run down the paper. Does the oil drop spread out in a thin layer Does the water stay together in a drop Does the oil drop move more slowly than a water drop The nonpolar oil is attracted to the nonpolar wax paper so it spreads out. The attraction between the oil drop and the wax paper makes the oil drop move more slowly than the water drop. The polar water is not attracted to the nonpolar wax paper so it stays in a drop. 

Soap molecules are very interesting because they are polar and nonpolar. A soap molecule is long. One end of the molecule is polar and the other end is nonpolar. When soap is added to water and oil, the nonpolar end of the soap molecule mixes with the nonpolar oil. The polar end of the soap molecule mixes with the polar water. This combination of polar and nonpolar molecules causes the mixture to be cloudy. Do you understand now why we use soaps and detergents to clean greasy messes ... 

Hydrophobic Compounds that are water fearing. Hydrophobic compounds do not dissolve easily in water and are usually nonpolar. Oils and other long hydrocarbons are hydrophobic. 

The aggregation behavior of AB silicone surfactants in nonpolar oils including several hydrocarbon oils has been reported by Rodriguez [46]. They found that inverse micelles were formed in all oils, adjacent to the inverse cubic phase formed by the neat copolymers and by concentrated mixtures of copolymer and oil. The CMC depended strongly on the length of the pEO chain but only weakly on the pDMS chain. Inverse hexagonal phase was also observed. 

Rodriguez, C., Uddin, M.H., Watanabe, K., Furukawa, H., Harashima, A. and Kunieda, H. (2002) Self-organization, phase behavior, and microstructure of poly(oxyethylene) poly(dimethylsiloxane) surfactants in nonpolar oil. /. Phys. Chem. B, 106(1), 22-9. 

The physical properties of supercritical fluids tend to lie between those of gases and liquids. The increased density relative to a gas, and the decreased viscosity relative to a liquid, allow supercritical fluids to be used as excellent solvents in many laboratory and industrial applications (19-25). Also, some notable solvation peculiarities of supercritical fluids have been discovered. For example, supercritical water can dissolve nonpolar oils because the dielectric constant of supercritical water decreases drastically near the critical point (26). 

Motor oil and water do not mix because the nonpolar oil molecules cannot displace the strong intermolecular attractions between water molecules. 

The mutual insolubility of nonpolar oil and very polar water leads to the common expression, Oil and water don t mix. ... 

Because nonpolar alkanes are not water soluble, crude petroleum spilled into the sea from a ruptured oil tanker creates an insoluble oil sUck on the surface. The insoluble hydrocarbon oil poses a special threat to birds whose feathers are coated with natural nonpolar oils for insulation. Because these hydrophobic oils dissolve in the crude petroleum, birds lose their layer of natural protection and many die. 

However, if you try to mix oil and water, the nonpolar oil molecules do not mix with the polar water molecules. The two liquids are immiscible. They form two layers, as shown in Figure 10b. The polar water molecules attract each other, so they cannot be pushed apart by the nonpolar oil molecules to form a solution. 

Nonpolar oil molecules do not mix with polar water molecules. Because oil is less dense than water, it floats on the water s surface. For this reason, oil spills at sea often wash ashore. 

The oil in Figure 15-5 is a substance made up of primarily carbon and hydrogen. It does not form a solution with water. Why are oil and water immiscible There is little attraction between the polar water molecules and the nonpolar oil molecules. However, oil spills can be cleaned up with a nonpolar solvent. Nonpolar solutes are more readily dissolved in nonpolar solvents. 

Consider the mixture resulting from vigorous shaking of salad oil (nonpolar) and vinegar (polar). Droplets of hydrophobic oil are temporarily suspended in the water. In a short time, however, the very polar water molecules, which attract one another strongly, squeeze out the nonpolar oil molecules. The oil then coalesces and floats to the top. If we add an emulsifying agent, such as egg yolk, and shake or beat the mixture, a stable emulsion (mayonnaise) results. 

It is also possible to prepare multiple emulsions consisting of nonpolar oil droplets with emulsified polar oil droplets which are dispersed in an aqueous solution or another polar oil. With W/O/W multiple emulsions it is essential to control the osmotic balance between the internal water droplets and the external... 

Emulsions are a class of disperse systems consisting of two immiscible liquids [1-3], whereby the Hquid droplets (the disperse phase) are dispersed in a liquid medium (the continuous phase). Several classes of emulsion may be distinguished, namely Oil-in-Water (O/W), Water-in-Oil (W/O), and OU-in-Oil (0/0). The latter class may be exemplified by an emulsion consisting of a polar oil (e.g., propylene glycol) dispersed in a nonpolar oil (paraffinic oil), and vice versa. In order to disperse two immiscible liquids a third component is needed, namely the emulsifier. The choice of the emulsifier is cmcial in the formation of an emulsion and its long-term stability [1-3]. 

Figure 14.24 shows a comparison of two nanoemulsions based on polydecene, a highly insoluble nonpolar oil and PPG-15 stearyl ether which is relatively more polar. Polydecene gave a low Ostwald ripening rate of 6.4 X 10 m s which was one order of magnitude lower than that of PPG-15 stearyl ether (5.5 x 10 m s ). 

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