Micellar dispersants

Son, M.O., r. "Hydraulic Fracturing of Subterranean Formations Using Hydrocarbon Micellar Dispersions," US Patent 3,603,400(1971). 

The diffuse part of the double layer is of little concern to us at this point. Chapters 11 and 12 explore in detail various models and phenomena associated with the ion atmosphere. At present it is sufficient for us to note that the extension in space of the ion atmosphere may be considerable, decreasing as the electrolyte content of the solution increases. As micelles approach one another in solution, the diffuse parts of their respective double layers make the first contact. This is the origin of part of the nonideality of the micellar dispersion and is reflected in the second virial coefficient B as measured by osmometry or light scattering. It is through this connection that z can be evaluated from experimental B values. 

For still larger quantities of water, one obtains the isotropic phase (IV), formed of mixed micelles. By extending the frontier line, WN, up to its intersection with side L-NaC of the triangle of the Figure 3, it can be seen that in order to get this micellar dispersion, at least one molecule of Na cholate is needed for two molecules of lecithin. 

These statements lead to the conclusion that the limiting proportion of 1 gram of Na cholate associated to 1 gram of lecithin is simply imposed by the size of a certain form of mixed micelle which can remain in equilibrium with an excess of Na cholate in micellar solution. Thus, it clearly appears that association is governed by the necessity of securing the proper hydrophilic-lipophilic balance of the mixture of two components. Here, as in the case of other amphiphilic substances, by the progressive increase in proportion of the more hydrophilic amphiphile. the association can reach complete micellar dispersion in water. 

Fig. 23. Variation of surface layer thickness with molecular weight of the stabilizing polydimethylsiloxane (PDMS) chain. Hydrodynamic thickness <5109) PMMA particles (O), PS particles ( ), micellar dispersions (A) from viscosity data x, thickness h from surface coverage data of PMMA particles assuming a prolate ellipsoid model for the...

NMR ( H, 13C), mass spectrometry, infrared (IR), and ultraviolet (UV) were used, especially NMR, in studying the complexation interactions of artemisinins with agents, such as /3-cyclodextrin <2004JPS2076> and micellar dispersions of octanoyl-6-O-ascorbic acid <2002JPS2265>. Furthermore, the structure-activity relationship of solution structures of deoxoartemisinin 10a and carboxypropyldeoxoartemisinin 10b, as antitumor compounds, was studied by H and 13C NMR <2000BBR359>. 

Viscosity and density of the component phases can be measured with confidence by conventional methods, as can the interfacial tension between a pure liquid and a gas. The interfacial tension of a system involving a solution or micellar dispersion becomes less satisfactory, because the interfacial free energy depends on the concentration of solute at the interface. Dynamic methods and even some of the so-called static methods involve the creation of new surfaces. Since the establishment of equilibrium between this surface and the solute in the body of the solution requires a finite amount of time, the value measured will be in error if the measurement is made more rapidly than the solute can diffuse to the fresh surface. Eckenfelder and Barnhart (Am. Inst. Chem. Engrs., 42d national meeting, Repr. 30, Atlanta, 1960) found that measurements of the surface tension of sodium lauryl sulfate solutions by maximum bubble pressure were higher than those by DuNuoy tensiometer by 40 to 90 percent, the larger factor corresponding to a concentration of about 100 ppm, and the smaller to a concentration of 2500 ppm of sulfate. 

An emulsion occurring between oil and water phases in a process separation or treatment apparatus. Such emulsions can have a high solids content and are frequently very viscous. In this case the term interface is used in a macroscopic sense and refers to a bulk phase separating two other bulk phases of higher and lower density. Other terms cufflayer , pad layer , or rag layer emulsions . An older term for the continuous (external) phase in micellar dispersions. See also Continuous Phase, Micelle. See Dispersed Phase. 

Griffin et al. (1988) reported that when the colloidal calcium phosphate was depleted, by addition of a EDTA solution to a micellar dispersion, there was essentially no selective dissociation of the individual caseins. This difference from the results of Holt et al. (1986) could reflect a difference of methodology. The method of Griffin et al. (1988) could bring about an almost complete and therefore non-selective disintegration of some micelles in the immediate vicinity of the added EDTA while leaving others virtually intact. In the dialysis method of Holt et al. (1986), the free Ca2+ concentrations is never depressed and hence micelles dissociate only because of the solubi-lazation of the colloidal calcium phosphate. 

The extremely low solubility of 1 (2.8 mg/1 in water and 0.77 mg/1 in 0.15 M NaCl at 23°) must certainly affect its bioavailabTlity on oral dosing of amounts wherein the solubility is exceeded. Tetrahydrocannabinol in excess of its solubility instantaneously forms a stable emulsion or micellar dispersion. Advantage can be taken of the high protein binding of 1 to administer plasma-solubilized solutions of 1 intravenously. ... 

A special case of - electrokinetic chromatography, in which the secondary phase is a micellar dispersed phase in the capillary. 

Jain S, Bates FS (2004) Consequences of nonergodicity in aqueous binary PEO-PB micellar dispersions. Macromolecules 37 1511-1523... 

A detailed study has been made of the action of pure triduoroacetic acid on cellulose and cellobiose (and their acetates). Dissolution of cellulose occurs, and swelling takes place with rupture of hydrogen bonds and with micellar dispersion esteridcation takes place without occurrence of degradation, the cellulose being fully recovered on hydrolysis of the triduoro-acetylated product. It appears that there is a more rapid rate of triduoro-acetylation of primary than of secondary alcohol groups. 

Pileni has also pioneered the use of the surfactant-as-reactant approach in the preparation of nanoparticles. For example, in the preparation of CoFc204 nanoparticles with sizes between 2 and 5 nm, instead of preparing inverse-micellar dispersions of the Co and Fe salts, Moumen and Pileni [48] prepared the dodecylsul-fonate (DS) analogs Fe(DS)2 and Co(DS)2. These were made to form micellar solutions, to raise the pH, aqueous methylamine solution was added. Stirring for 2 h resulted in a magnetic precipitate. Due to the low yield of Fe(II) to Fe(III) oxidation under these conditions, an excess of Fe(DS)2 is required. 

Simple micellar dispersed solutions are also directly usable by the experimenter. 

The advantage of the microemulsion-based route is that it is a soft technique, i.e. it does not require extreme conditions of pressure and temperature. But it is the dynamic of micellar dispersions that makes themso relevant for this kind of purpose the droplets are indeed subject to Brownian motion and collide continuously, leading to the formation of short-lived dimers and to the exchange of the aqueous contents of the micelles. This dynamic process ensures a homogeneous repartition of the reactants among the aqueous droplets or water pools and thus the formation of very monodispersed particles [3]. 

For the micellar dispersant giving a dispersion a conductivity of 10- ohm-lcm l the frictional coefficient is found to be 10 dynes cm l sec (11), which corresponds to n=4xl0l6 ionic micelles per cubic centimeter or 65 micromoles per liter. The Debye length 1/k is calculated to be 59°, using e c kT O/o... 

Figure 2. Electrostatic energy barrier between two carbon particles in oil with micellar dispersant. Conditions ip0, —ISO mV 1/k, 59A

Bueno, C.A., Silva, E., and Edwards, A.M. (1999) Incorporation and photodegradation of flavin and indole derivatives in anionic, cationic and neutral micellar dispersions, J. Photochem. Photobiol. B-Biol., 52, 123-130. 

Up till now intestinal lipid absorption from mixed micellar solutions has been studied in detail. The existence of non-micellar dispersions of lipolytic products in intestinal contents during fat digestion has recently been proposed [18,47], but so far only little information regarding the importance of these phases for the lipid... 

Data on absorption of non-micellar lipids in the presence of bile salts is available from the study )y Knoebel [79]. The lymphatic transport of absorbed oleic acid and site of uptake from the intestinal lumen was measured in bile fistula rats. It was found that the concentration of bile salts in a continuous intraduodenal infusion did not affect the steady-state level of lipid appearing in the lymph until the bile salt concentration was as low as 1 mM, which represented a molar ratio of 20 1 of lipid to bile salt. In the case of infusates with relatively low concentrations of bile salts it was found that a larger part of the available surface area of the small intestine was utilized. The main conclusion is that lipids are equally well absorbed in vivo from non-micellar dispersions of lipids and bile salts as from solutions where the lipids are completely solubilized by bile salt mixed micelles. However, a detailed analysis of kinetics of uptake from non-micellar phases in vitro with isolated intestinal segments has not yet been done. 

It thus is generally accepted that micellar dispersion rather than lipolysis is the rate-limiting step in bile deficiency that results in partial malabsorption. 

Micellar dispersions, which contain micelles along with individual surfactant molecules, are the typical examples of lyophilic colloidal systems. Micelles are the associates of surfactant molecules with the degree of association, represented by aggregation number, i.e. the number of molecules in associate, of 20 to 100 and even more [1,13,14]. When such micelles are formed in a polar solvent (e.g. water), the hydrocarbon chains of surfactant molecules combine into a compact hydrocarbon core, while the hydrated polar groups facing aqueous phase make the hydrophilic shell. Due to the hydrophilic nature of the outer shell that screens hydrocarbon core from contact with water, the surface tension at the micelle - dispersion medium interface is lowered to the values othermodynamic stability of micellar systems with respect to macroscopic surfactant phases. 

Under particular conditions the thermodynamically stable micellar dispersions may form as a result of spontaneous dissolution of crystalline or liquid surfactant macroscopic phase. Even though the state of substance in a micelle is not always equivalent to that in a macrophase, a rather high degree... 

Intermicellar Liquid An older term for the contiuous (external) phase in micellar dispersions. See also Continuous Phase, Micelle. 

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