Micellar solubilization

Why is co-crystal behavior in micellar surroundings relevant Is it different from the behavior of single component crystals The answer to the first question is that mastery of co-crystal properties depends on our ability to understand its interactions with the surrounding media. The answer to the second question is that every co-crystal component plays an important role on cocrystal behavior and this combination can be quite different from those of the individual component crystal phases. 

Micelles are nano or micro structures with a hydrophobic core and a hydrophilic shell. They form above a eritieal eoneentration called the eritical micellar concentration (CMC) as a result of the self-association of amphiphilic molecules to minimize hydrophobic interactions. Micellar surfactants and polymers are widely used in the pharmaceutical industry as formulation aids in solids, semi-solids, suspensions, emulsions, and solutions. One of the 

The co-crystal solubility, 5 rha,t, under stoichiometric conditions, is equal to the total concentration of each co-crystal component in equilibrium with solution  

The contribution of micellar solubilization of the drug component R to the co-crystal solubility is given by  

Co-crystal solubility can be expressed in terms of surfactant micellar concentration, co-crystal and micellar solution equilibrium constants as  

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Other solubilization and partitioning phenomena are important, both within the context of microemulsions and in the absence of added immiscible solvent. In regular micellar solutions, micelles promote the solubility of many compounds otherwise insoluble in water. The amount of chemical component solubilized in a micellar solution will, typically, be much smaller than can be accommodated in microemulsion fonnation, such as when only a few molecules per micelle are solubilized. Such limited solubilization is nevertheless quite useful. The incoriDoration of minor quantities of pyrene and related optical probes into micelles are a key to the use of fluorescence depolarization in quantifying micellar aggregation numbers and micellar microviscosities [48]. Micellar solubilization makes it possible to measure acid-base or electrochemical properties of compounds otherwise insoluble in aqueous solution. Micellar solubilization facilitates micellar catalysis (see section C2.3.10) and emulsion polymerization (see section C2.3.12). On the other hand, there are untoward effects of micellar solubilization in practical applications of surfactants. Wlren one has a multiphase... 

Petroleum sulfonates are widely used as solubilizers, dispersants (qv), emulsifiers, and corrosion inhibitors (see Corrosion and corrosion inhibitors). More recentiy, they have emerged as the principal surfactant associated with expanding operations in enhanced oil recovery (66). Alkaline-earth salts of petroleum sulfonates are used in large volumes as additives in lubricating fluids for sludge dispersion, detergency, corrosion inhibition, and micellar solubilization of water. The chemistry and properties of petroleum sulfonates have been described (67,68). Principal U.S. manufacturers include Exxon and Shell, which produce natural petroleum sulfonates, and Pilot, which produces synthetics. 

Instead of applying synthetic methods to alter chromophore reactivity, this new way of controlling chemical reactivity involves choosing an appropriate solid micellar system (from the available multitude) and exploiting it to manipulate the chemistry of the entrapped compound. The sol-gel matrix and the micellar solubilization, in fact, have a synergetic effect. Their combination produces effects stronger and more tuneable than in solution, so that a careful selection of sol-gel entrapped surfactants allows one to induce enormous changes in the dopant properties. 

In the SDS solutions containing 0.1-0.4 M NaCl, the turbidity increase is mainly due to micellar solubilization. The solubilization rate (di/dt) of the solutions seems to be in this order 0.1M> 0.2M> 0.3M> 0.4M NaCl. The final solubilization of the solutions is also in the same order. The size of the pure SDS micelles in solutions containing NaCl has been shown to increase with the NaCl concentration (Table II). Our instrument is not sensitive enough to distinguish the size between these small micelles at different NaCl concentrations. In the solubilization of oleic acid in 0.5% SDS solutions, the maximum seems to occur when the NaCl concentration is around 0.1 M. 

Since oleic acid is relatively polar, it may become emulsified by the surfactant monomer. The removal of oleic acid comes mainly from two contributions monomer emulsification and micellar solubilization. Although the Vgjj has been decreased with increasing EO number in dodecanol ethoxylates, in higher EO numbers than 5, this factor has been compensated by the Increase of monomer with increasing EO number (CMC decreases with EO number). The levelling of detergency of dodecanol ethoxylates from EO number 5 to EO number 8 has been interpreted by these reasons. The monomer emulsification of oleic acid has been clearly shown in this paper in SDS solution. The nonionic surfactants we used here have low EO numbers and show mainly the effect of solubilization. 

SCHWAB AND PRYDE Micellar Solubilization of Methanol and Triglycerides 285... 

Barbaric, S. and Luisi, P. L. (1981). Micellar solubilization of biopolymers in organic solvents. 5. Activity and conformation of a-chymorypsin in isooctane-AOT reverse micelles. J. Am. Chem. Soc., 103,4239 4. 

A totally different way of looking at microemulsions —and one that connects this topic with previous sections of the chapter —is to view them as complicated examples of micellar solubilization. From this perspective, there is no problem with spontaneous formation or stability with respect to separation. Furthermore, ordinary and reverse micelles provide the basis for both O/W and W/O microemulsions. From the micellar point of view, it is the phase diagram for the four-component system rather than y that holds the key to understanding microemulsions. 

Bury, S. J. Miller, C. A. (1993). Effect of micellar solubilization on biodegradation rates of hydrocarbons. Environmental Science Technology, 27(1), 104—10. 

It has been well documented that surfactants self-associate in aqueous solution to minimize the are of contact between their hydrophobictails and the aqueous solution (Mukerjee, 1979 Tanford, 1980). This phenomenon occurs at a critical concentration of surfactant, the critical micelle concentration or CMC (see Figure 12.4) above where the surfactant molecules exist predominantly as monomeric units and above which micelles exist. The CMC can be measured by a variety of techniques, for example, surface tension, light scattering, osmometry, each of which shows a characteristic break point in the plot of the operative property as a function of concentration. Knowing the CMC of the particular surfactant system and understanding the conditions that may raise or lower that critical concentration is important to the design of a formulation based on micellar solubilization. 

Factors Affecting Micellization and Micellar Solubilization Temperature... 

Temperature has a major impact on micellization and micellar solubilization. As discussed in the section of temperature-composition phase diagram, change in micellar size due to changes ir... 

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