Miscibility of fluorocarbons

Alternatively, we have shown that CO2 can be used to induce miscibility of fluorocarbon-hydrocarbon mixtures (see Figure 1), even those involving polar compounds such as methanol (2). Fluorinated organometallic complexes have been well established to have significant solubility in supercritical CO2, and their use as catalysts in this medium is well developed (10). This allows the homogeneously catalyzed reaction to be carried out in the C02-expanded homogeneous solution. 

The Hilderbrand-Scatchard solubility parameter 8 (Equation 16.1) can be used to estimate the miscibility of fluorocarbons with organic solvents [11-13],... 

Further, we have observed that ANS is not solubilized into fluorocarbon surfactant micelles, so the miscibility of the fluorocarbon and hydrocarbon surfactants can be studied by using the fluorescence probe, ANS. 

The extensive studies of the behavior of mixed monolayers or bilayers of di-acetylenic lipids and other amphiphiles parallel to some degree the studies of dienoyl-substituted amphiphiles. Since the dienoyl lipids do not contain a rigid diacetylenic group in the middle of the hydrophobic chains, they tend to be miscible with other lipids over a wide range of temperatures and compositions. In order to decrease the lipid miscibility of certain dienoyl amphiphiles, Ringsdorf and coworkers utilized the well-known insolubility of hydrocarbons and fluorocarbons. Thus two amphiphiles were prepared, one with hydrocarbon chains and the other with fluorocarbon chains, in order to reduce their ability to mix with one another in the bilayer. Of course it is necessary to demonstrate that the lipids form a mixed lipid bilayer rather than independent structures. Elbert et al. used freeze fracture electron microscopy to demonstrate that a molar mixture of 95% DM PC and 5% of a fluorinated amphiphile formed phase-separated mixed bilayers [39]. Electron micrographs showed extensive regions of the ripple phase (Pb phase) of the DM PC and occasional smooth patches that were attributed to the fluorinated lipid. In some instances it is possible to... 

The almost universal chemical inertness of polytetrafluoroethylene has been attributed to the strength of the carbon-fluorine bond and the way in which the fluorine atoms protect the carbon chain from chemical attack (Doban, Sperati, and Sandt). From the theory of solubility, it is expected that the miscibility of hydrocarbons and fluorocarbons will be low. Experimental measurements indicate that the miscibility is even less than was expected from the theory. The possible explanations for this have been discussed by Scott. 

Mukerjee, P. and Yang, A.Y.S., Nonideality of mixing of micelles of fluorocarbon and hydrocarbon surfactants and evidence of partial miscibility from differential conductance data, J. Phys. Chem., 80, 1388, 1976. 

The most effective emulsion and foam stabilizers are aerosol systems containing fluorocarbon propellants as surfactants. These are believed to form an oriented polymolecular structure at the propellant-water interface for optimum stability Sanders has found [90] that the surfactants must have a low solubility in both phases and have the ability to remain in the interfacial region. Hydrocarbon and fluorocarbon chains are not freely miscible and this perhaps explains the unusual behaviour of the surfactants in these systems. Addition of long-chain alcohols or acids enhance stability of the fluorocarbon emulsions and a hypothetical structure of the interfacial region has been proposed (Fig. 8.16). Davis et al. [91] have investigated the stability of fluorocarbon emulsions intended as artificial blood substitutes. Perfluorocarbon oils tended to produce unstable emulsions while oil phases such as perfluorotributylamine or per-fluorotetrahydrofuran formed more stable systems. These authors also refer to the possibility that as fluorocarbon-hydrocarbon mixtures have positive excess free energies, cohesive and adhesive forces between surfactant and oil phase will result. 

The pseudophase separation model of micellar solutions considers a micelle to be a pseudophase in a liquid state. Because the micelles are assumed to have a liquidlike core, the mutual solubility of a fluorinated surfactant and a hydrocarbon surfactant in mixed micelles is, according to the pseudophase model, governed by the miscibility of the fluorocarbon and hydrocarbon chain. For example, heptane and perfluoroheptane are immiscible at 25°C, but above 50°C, these liquids are miscible in all proportions [75]. A terminal substitution of a hydrophilic group depresses the enthalpy of mixing and makes the components miscible at 25°C. 

The mutual miscibility of anionic fluorinated surfactants and hydrocarbon surfactants increases with increasing temperature, similar to the miscibility increase of fluorocarbon and hydrocarbon liquid mixtures [76,120]. In the LiFOS-LiTS system, the solubility of LiFOS increased substantially in the LiTS-rich micelle but only slightly in the LiFOS-rich micelle [99]. In comicellar systems, such as NF-STS [112] and LiFOS-LiDS [76], the temperature dependence of mutual miscibility exhibits a critical solution temperature (cst) that corresponds to the transition from two types of micelle to one type of mixed micelle. Above the cst, only one kind of mixed micelle exists below the critical solution temperature (cst), two types of micelles can coexist. 

The miscibility between hydrocarbon and fluorocarbon surfactants was studied by means of a steady-state fluorescence. Three mixed aqueous solutions of surfactants were employed sodium dodecyl sulfate (SDS)-p-t(CF )2CF]2C=C(CFj)0(CH CH O) -CH (NF), hexaoxyethylene-... 

M. Amadori studied fused mixtures of sodium fluoride and carbonate no compound is formed, and the salts are not miscible in the solid state. There is a eutectic at 690° and 39 mols. per cent, sodium fluoride. Similar results obtain with sodium chloride and carbonate. There is an eutectic at 636° and 59 mols. per cent, of sodium chloride. Similarly, with potassium fluoride and carbonate, there is with a eutectic at 636° and 65 mols. per cent, of potassium chloride. With the system potassium fluoride and carbonate there is a eutectic at 688° with nearly 46 mols. per cent, of potassium fluoride, and another eutectic at 682° with 62 mols. per cent, of potassium fluoride there is a slight rise in the m.p. between the two eutectics, corresponding with the formation of potassium fluorocarbonate, KF.K2C03. 

Difluoroethane is useful as an aerosol propellant in that it shows greater miscibility with water than some other fluorocarbons and when combined with chlorodifluoroethane will produce a mixture with a specific gravity of 1. For a discussion of the numerical nomenclature applied to this aerosol propellant, see Ghlorofluorocarbons. 

Perfluorinated alkanes, dialkyl ethers, and trialkylamines are unusual because of their nonpolar nature and low intermolecular forces. Their miscibility, even with common organic solvents such as toluene, THF, acetone, and alcohols, is low at room temperature, so these materials could form fluorous biphase systems [2]. The term fluorous was introduced [4, 5], as the analog to the term aqueous, to emphasize the fact that one of the phases of a biphase system is richer in fluorocarbons than the other. Fluorous biphase systems can be used in stoichiometric... 

Solvents used in aerosol cans (spray cans for hair lacquer, cleansing agents, paints) must, of course, dissolve the substances that are to be sprayed. They must also be miscible with the propellants without causing the dissolved substance to precipitate. Previously, chlorofluorohydrocarbons were mainly used as propellants but they have a damaging effect on the stratospheric ozone layer and have now been largely replaced by alternatives (e.g., hydrocarbons such as butane, diethyl ether, fluorocarbons, carbon dioxide) [14.260]. 

UFe. In complete contradiction to the predictions of the existing liquid mixture theory it was found that these fluorocarbons were only partially miscible with hydrocarbons of comparable molar mass. The large volume of experimental work that resulted from attempts to interpret this unexpected behaviour of mixtures consisting of relatively simple non-polar molecules is covered comprehensively in Scott s 1958 review. ... 

The solubility of the solvents in T able 17.1.1 ranges from those that are miscible with water to those with solubilities that are less than 0.1 mg/L (Table 17.1.2). Acetone, methanol, pyridine and tetrahydrofuran will readily mix with water in any proportion. The solvents that have an aqueous solubility of greater than 10,000 mg/L are considered relatively hydrophillic as well. Most of the benzene derivatives and chlorinated fluorocarbons are relatively hydrophobic. Hexane and decane are the least soluble of the 31 solvents in Table 17.1.1. Most material safety data sheets for decane indicate that the n-aUcane is insoluble and that the solubility of hexane is negligible. How the solubility of each solvent affects its fate in sod, water, and air is illustrated in the following sections. 

The concept of fluorous biphase hydroformylation of heavy olefins was introduced by Horvath at Exxon in 1994 [42, 43]. Fluorocarbon-based solvents, especially perfluorinated alkanes and ethers, are of modest cost, chemically inert, and nonpolar and show low intermolecular forces. Most of them are immiscible with water and can be therefore used as the nonaqueous phase. Moreover, their miscibility with organic solvents such as toluene, THF, or alcohols at room temperature is quite low. Only at elevated temperature miscibility occurs. These features allow hydroformylation at smooth reaction conditions at 60-120 °C in a homogeneous system [44]. Upon cooling, phase separation takes place. The catalyst is recovered finally by simple decantation. One of the last summaries in this area was given by Mathison and Cole-Hamilton in 2006 [45]. 

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