Micelle Results

The monomers get absorbed in micelles resulting in their swelling. Water soluble initiators are used which form free radicals. Inorganic persulphates are commonly used as initiators. The initiator diffuses into a micelle and polymerisation proceeds. As more monomer is polymerised monomers from outside the micelle diffuse inside and the process continues when another radical enters the micelle the polymerisation stops. This technique can give high Molecular weight polymers. 

The reduction of the ionization potential in micelles results from solvation effects on the cation and on the electron, and also the surface energy. These are sufficient to drop the ionization potential by as much as 4 volts. 

The critical micelle concentration (c.m.c.) of the material increases with decrease in pH of the solution below 5, as is to be expected as the ratio of to B- increases. The increase in the c.m.c. is somewhat greater than the increase in the C20 value with pH decrease as shown by the cmc/C2o ratio, indicating somewhat greater inhibition of micellization than of adsorption at the aqueous solution/air interface as the BHVB- ratio increases. This may reflect some steric inhibition of micellization resulting from the increased size of the protonated hydrophilic head. 

Most of the characteristics invoked to explain rate accelerations and rate retardations by micelles are valid for vesicles as well. For example, the alkaline hydrolysis of A-methyl-A-nitroso-p-toluenesulfonamide is accelerated by cationic vesicles (dioctade-cyldimethylammonium chloride). This rate acceleration is the result of a higher local OH concentration which more than compensates for the decreased polarity of the vesicular pseudophase (compared to both water and micelles) resulting in a lower local second-order rate constant. Similar to effects found for micelles, the partial dehydration of OH and the lower local polarity are considered to contribute significantly to the catalysis of the Kemp elimination " by DODAB vesicles. Even the different... 

MEKC is also performed using cationic, nonionic, and zwitterionic surfactants. Widely employed are cationic surfactant consisting of a long chain tetralkylammonium salt, such as cetyltrimeth-ylammonium bromide, which causes the reversal of the direction of the EOE, due to the adsorption of the organic cation on the capillary wall. Other interesting options include the use of mixed micelles resulting from the simultaneous incorporation into the BGE of ionic and nonionic or ionic and zwitterionic surfactants. Chiral surfactants, either natural as bile salts [207] or synthetic [208] are employed for enantiomer separations. 

Surfactants having an appropriate hydrophobic/hydrophilic balance (sodium bis(-2-ethylhexyl)sufosuccinate, or AOT, for example) undergo concentration-dependent self association in apolar solvents to form reversed or inverted micelles (Fig. 33) [256-262]. Reversed micelles are capable of solubilizing a large number of water molecules (AOT reversed micelles in hexane are able to take up 60 water molecules per surfactant molecule, for example). Reversed-micelle-entrapped water pools are unique they differ significantly from bulk water. At relatively small water-to-surfactant ratios (w = 8-10, where w = [H20]/[Surfactant]), all of the water molecules are strongly bound to the surfactant headgroups. Substrate solubilization in the restricted water pools of reversed micelles results in altered dissociation constants [256, 257, 263-265], reactivities [256, 258, 266], and reaction products [267]. 

Many reduce bioavailability at low doses for drugs with solubility-limited absorption (drug partitioning into micelle, resulting in lower concentration of the free drug)... 

In simple terms, in aqueous media, micelles result in hydrophobic domains within the solution whereby the surfactant may solubilise or emulsify particular solutes. Hence, surfactants will modify solution properties both within the bulk of the solution and at interfaces. 

Microviscosity effects inside a micelle result from an unusually higher viscosity in a micelle than the overall viscosity of the solution. This phenomenon leads to modification of photochemical reactions which are sensitive to viscosity. The microviscosity in common micelles composed of ionic detergent typically vary from 15 cP to 100 cP. In some cases, the viscosity effect on a reaction can be used to calibrate the microviscosity of micelles. 

In making yogurt, milk is initially heated at SO C for 15-30 min in order to denature the mhey proteins. This heating provokes the whey proteins to denature, and consequently associate with the casein micelles, resulting in a yogurt with improved viscosity and texture (Law and Leaver, 1997 Boyeef jiL, 1997 Ottecl ai, 1996). 

Other conversion methods depend on the disruption of micelles containing water-insoluble compounds. For example, lipids e.g. lecithins can be reasonably well cosolubilized in micelles of sodium cholate or SDS. Dialysis slowly removes monomeric detergent molecules which dissociate away from the micelle resulting in a more concentrated lipid. Time and temperature controlled dialysis of the micelles finally yields monolamellar vesicles of uniform radii. ... 

Figure shows electropherograms of a mixture of five barbiturate standards it can be observed that the addition of micelles in MEKC clearly resulted in a different separation mechanism, reflected in various changes in elution order, compared to CZE. The migration behavior in MEKC depends largely on the hydro-phobic interaction of the analytes with the micelles. Hydrophobic components are more solubilized in the micelles, resulting in a slower migration compared to less hydrophobic compounds. 

H2O molecules to be coordinated to Eu in the absence of substrate. Addition of a monomeric substrate reduced this number by one. Binding of the enzyme-Eu " complex to micelles results in nearly complete dehydration of Eu " at the catalytic center. This dehydration could be an important reason for the enhanced activity of this enzyme at the lipid-water interface. 

This formation of ordered an assembly of micelles results in a higher rate of hydroformylation and increased selectivity to the linear aldehyde. Effects of operation... 

From the above discussion it is evident that the primary action of proteases on the casein system is fairly well understood. But how this primary action alters the functionality of the casein micelles resulting in micellar coagulation is incompletely understood and will require further research. 

The formation of micelles results in a sharp drop in the electrical conductivity per mole of the electrolyte. Suppose 100 sodium and 100 stearate ions were present individually. If the stearate ions aggregate into a micelle and the micelle binds 70 Na as counter ions, then there will be 30 Na ions and 1 micellar ion having a charge of —30 units a total of 31 ions. The same quantity of sodium stearate would produce 200 ions as individuals but only 31 ions if the micelle is formed. This reduction in the number of ions sharply reduces the conductivity. The formation of micelles also reduces the osmotic pressure of the solution. The average molar mass, and thus an estimate of the average number of stearate ions in the micelle, can be obtained from the osmotic pressure. 

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