Micelle apparent charge

The Apparent Charge of Ionic Micelles in Aqueous Binary Solvents... 

The aim of most authors (3,11,12) in using Equations 2, 3, 4, or 5 was to predict from a given model the variation of the cmc with solvent composition. To our knowledge, however, except in a few cases (3,4), AGt° was ignored and the electric potentials were calculated with drastic simplifications e.g., the variation of the apparent charge of the micelle with the addition of the organic component was not taken into account. There is no easy way of determining the composition X of the mixed micelle, so we shall focus our discussion on the simplest case, i.e. that described by Equation 5. 

The main goal will be the determination of the apparent charge of the micelle in the binary aqueous solvents. Contradictory findings are found in the literature when the apparent charge is deduced from emf determinations (12,13). We shall discuss these results and compare them with those obtained using a conductivity approach. 

Variation of the Critical Micelle Concentration and Apparent Charge of the Micelles in the Mixed Solvents... 

Table V and Figures 4, 5, and 6 present our essential results. Figures 4 and 5 show the relative magnitude of each term of Equation 5, the electric potential term being represented by the difference between the two curves for AGt° and 2RT In (cmcwf w)/(cmc8f 8). Figure 6 shows that the number of monomers per micelle n decreases rapidly with the addition of acetone for both surfactants as could be expected although the rate of the change of n could not be predicted more important is the very small change of the apparent charge of the micelle Z(mic) with the...

Figure 6. Variation of the apparent charge of the ionic micelles with solvent composition Zmic = an...

The MW descriptions of the membranes in hexane may not be applicable because of swelling and the changes in the surface chemistry of the polymers used. A sizable reduction in flow rates may be observed with hexane-oil miscellas. The stability of micelles apparently is a function of solvent type, charges and location of the phosphorous group, and specific impurities of the crude oil. 

The anion series in the order of their influence on the surface activity of cationic surfactants and on the properties of insoluble monolayers coincide with the lyotropic series. The anion nature is manifested in the specific interaction with cationic surfactants with the formation of ionic pairs or in the anion penetration into the adsorption monolayers. Apparently, charge transfer complexes are frequently formed at the water-air and water-oil interfaces between the adsorbed cations and anions. Mukerjee and Ray estabhshed that these complexes exist in ionic pairs, between Br or J anions and dodecylpyridine ions in chloroform, and also on the micelle surface formed by the same cations in water [84-86]. The data on the ionic pair structure at the interface can be obtained by spectral study of monolayers and solutions of ionogenic surfactants in nonpolar solvents. According to Goddard, the investigation on the mixed monolayers formed by the surface-active anions and quaternary ammonium compounds will enable us to better understand the specific properties of the interaction between the adsorbed ions [72]. 

If /(, ,j is the micelle aggregation number and the apparent charge of the micelle, the concentrations of the various constituents are ... 

From the apparent ionization degree it was concluded that the EO chain probably behaves as part of the headgroup. As with Aalbers [49], a low surface charge of the sodium alkyl ether carboxylate micelles was mentioned. The micelle aggregation number N increases with the C chain much more than for the corresponding nonionic surfactants. In the case of C8 there was no influence of temperature. A small decrease was found with increasing EO, but much smaller than in the case of nonionics. 

The effect of micelles on these spontaneous hydrolyses is difficult to explain in terms of kinetic solvent effects on these reactions. Mukerjee and his coworkers have refined earlier methods for estimating apparent dielectric constants or effective polarities at micellar surfaces. For cationic and zwitterionic betaine sulfonate micelles Def is lower by ca 15 from the value in anionic dodecyl sulfate micelles (Ramachandran et al., 1982). We do not know whether there is a direct connection between these differences in effective dielectric constant and the relation between reaction rates and micellar charge, but the possibility is intriguing. 

One consequence of roughness at the surface of the micellar core is an increased contact between water and hydrocarbon. Figure 8.3b seems unrealistic because the water-hydrocarbon contact is scarcely less than in the bulk solution, a situation that apparently undermines an important part of the driving force for micellization. Figure 8.3c minimizes this effect without eliminating it. At the same time it allows for some water entrapment, which accounts for that part of the micellar hydration that was unexplained by the hydration of ions and charged groups. 

Shinoda examined the variation of the CMC of various potassium alkyl malonates, RCH(COOK)2, with the addition of univalent salts. For R = C8, C,2, CM, and C16, the log-log plots of CMC verus counterion concentration produce parallel straight lines of slope -1.12. Criticize or defend the following proposition According to the analysis presented in Example 8.1, the slope of this type of plot equals —(1 — a), meaning that a = —0.12 this negative function apparently means that the micelle binds an excess of counterions and has the opposite charge from that expected. 

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