Effect of surfactant micelles

The Effect of Surfactant Micelles on the Yields Obtained In Electrooxidations on Platinum Electrodes In 2M Aqueous Sodium Hydroxide ... 

Harada T, Nishikido N, Moroi Y, Matuura R. Effect of surfactant micelles on the rate of reaction of tetranitromethane with hydroxide ion. Bull Chem Soc pn 1981 54 2592-2597. 

Several reports exist on the effect of metal cations on satin hydrolysis (Wagner-Jauregg et al., 1955 Gustafson and Martell, 1962 Epstein and Mosher, 1968). Some of the metal ions that appear to be effective include Cu(ll), Au(ll), Ag(l), Ni(ll), and Zn(ll). The effect of hypochlorite on sarin decomposition has been studied (Epstein et al., 1956), including the effect of surfactant micelles on the process (Dubey et al., 2002). It was shown that the use of cetyltrimethylammonium bromide substantially increased the speed with which satin was destroyed by hypochlorite. The effect of surfactant on the oxidation of sarin (and other OPs) with o-iodosobenzoic acid has been examined (Hammond et al., 1989). As part of an extensive study of the reactivity of nerve agents, Larsson (1958a) conducted a study of hydrogen peroxide s reaction with sarin. 

The obstruction effect a physical effect of surfactant micelles... 

The energetics and kinetics of film formation appear to be especially important when two or more solutes are present, since now the matter of monolayer penetration or complex formation enters the picture (see Section IV-7). Schul-man and co-workers [77, 78], in particular, noted that especially stable emulsions result when the adsorbed film of surfactant material forms strong penetration complexes with a species present in the oil phase. The stabilizing effect of such mixed films may lie in their slow desorption or elevated viscosity. The dynamic effects of surfactant transport have been investigated by Shah and coworkers [22] who show the correlation between micellar lifetime and droplet size. More stable micelles are unable to rapidly transport surfactant from the bulk to the surface, and hence they support emulsions containing larger droplets. 

Effects of Surfactants on Solutions. A surfactant changes the properties of a solvent ia which it is dissolved to a much greater extent than is expected from its concentration effects. This marked effect is the result of adsorption at the solution s iaterfaces, orientation of the adsorbed surfactant ions or molecules, micelle formation ia the bulk of the solution, and orientation of the surfactant ions or molecules ia the micelles, which are caused by the amphipathic stmcture of a surfactant molecule. The magnitude of these effects depends to a large extent on the solubiUty balance of the molecule. An efficient surfactant is usually relatively iasoluble as iadividual ions or molecules ia the bulk of a solution, eg, 10 to mol/L. 

The catalytic activity of surfactant micelles and the effect of the concentration of reagents in micelle catalysis are tested on hydrolysis of esters of phosphorus acids [25],... 

N-Alkylhydroxamic acid hydrolysis Methyl Violet + OH" Cl C12H25S03Na + H30+, CTABr + OH". An attempt made to separate electronic and hydrophobic effects on the micellar reaction Anionic and cationic micelles. Effect of surfactant structure examined Berndt el at., 1984 Malaviya and Katiyar, 1984... 

Calorimetric measurements can be used to obtain heats of mixing between different surfactant components in nonideal mixed micelles and assess the effects of surfactant structure on the thermodynamics of mixed micellization. Calorimetry can also be successfully applied in measuring the erne s of nonideal mixed surfactant systems. The results of such measurements show that alkyl ethoxylate sulfate surfactants exhibit smaller deviations from ideality and interact significantly less strongly with alkyl ethoxylate nonionics than alkyl sulfates. 

Effect of surfactant type and concentration An increase in surfactant concentration results in an increase in the number of micelles rather than any substantial change in size, and this enhances the capacity of the reverse micelle phase to solubilize proteins. Woll and Hatton [24] observed increasing protein solubilization in the reverse micelle phase with increasing surfactant concentration. In contrast, Jarudilokkul et al. [25] found that at low minimal concentrations (6-20 mmol dm AOT), reverse mieelles eould be highly seleetive in separating very similar proteins from... 

Partition coefficients of surfactants have been reported to remain constant below the critical micelle concentration (CMC), and to increase with concentration above the CMC (2,9,10). The effect of surfactant concentration in the aqueous phase (C ) on K was investigated with Makon 14 (14 mol% ethylene oxide, NPEj ), the results are given in Fig. 2. These data indicate a CMC of about O.lg/1, or 12 piM, in close agreement with the value obtained by surface tension measurements (our data and ref. 22). In subsequent determinations of Kp, C was just below the CMC to minimize the effects of micellization (15,23). 

Introduction to the variety of types of surfactants, effect of surfactants on aqueous solution properties. Law of mass action applied to the self-assembly of surfactant molecules in water. Spontaneous self-assembly of surfactants in aqueous media. Formation of micelles, vesicles and lamellar structures. Critical packing parameter. Detergency. Laboratory project on determining the charge of a micelle. 

The effect of surfactant concentration on critical osmotic pressure was also studied [97], Below a critical surfactant concentration, emulsions are always unstable due to incomplete coverage of the oil-water interfaces. Above this, Jt increases with increasing surfactant concentration until the critical micelle concentration (CMC) is reached, above which it remains more or less constant. 

Reversed micelle-entrapped, colloidal CdS showed the characteristic weak fluorescence emission (Figure 2), previously observed in homogeneous solutions (16-19). However, the maximum emission intensity corresponded to full band gap emission (approximately 500 nm) and was not red-shifted as observed in homogeneous solution (17). This discrepancy might arise from the mode of prep>aration (H S instead of Na S), or from the specific effect of surfactant aggregates. 7 lternatively, tras can be the result of a size... 

A study of the effects of surfactants on the reaction of 2-(4-cyanophenoxy)quinoxa-line with hydroxide ions has shown that rate accelerations caused by cetyltrialkylam-monium chlorides may be due to reaction in premicellar aggregates or in micelles.54... 

The effects of surfactant on the solubility and dissolution rate of poorly soluble drugs are well characterized. In general, the surfactant increases both solubility and dissolution rate even if the increment in dissolution rate is less pronounced due to the low diffusivity of the drug loaded into the micelle [9-16]. 

The characteristic effect of surfactants is their ability to adsorb onto surfaces and to modify the surface properties. Both at gas/liquid and at liquid/liquid interfaces, this leads to a reduction of the surface tension and the interfacial tension, respectively. Generally, nonionic surfactants have a lower surface tension than ionic surfactants for the same alkyl chain length and concentration. The reason for this is the repulsive interaction of ionic surfactants within the charged adsorption layer which leads to a lower surface coverage than for the non-ionic surfactants. In detergent formulations, this repulsive interaction can be reduced by the presence of electrolytes which compress the electrical double layer and therefore increase the adsorption density of the anionic surfactants. Beyond a certain concentration, termed the critical micelle concentration (cmc), the formation of thermodynamically stable micellar aggregates can be observed in the bulk phase. These micelles are thermodynamically stable and in equilibrium with the monomers in the solution. They are characteristic of the ability of surfactants to solubilise hydrophobic substances. 

Little and Singleterry (7) have published an interesting study on micellization of surfactants in a variety of solvents. Their data show that the better the solvent is for the surfactant, the less tendency there is for the surfactant to form aggregates or micelles. Yet to be determined is the effect of this micellization on emulsification properties. 

The authors have studied the effects of some surfactants on the rate of interfacial transfer this work, which has not been published, has shown that the rate may be increased or decreased. The structure of the surfactant is important, and the effects apply both above and below the critical micelle concentration of the surfactant. The effect in certain cases was to impede transfer totally, which suggests that much more work is required to build up an understanding of the properties of biological systems, and of the effects of surfactants on them. Surfactants are commonly present in pesticide formulations. 

The available data on the effects of surfactants and micellization on the hydrolysis of carboxylic esters are compiled in Table 5. 

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