Degree of micellar ionization

The micelles act as a separate phase they are uniformly distributed throughout the solution and are invariant in composition throughout the micellar range. The degree of counterion ionization remains constant irrespective of ion type or concentration or of surfactant concentration. 

Van Paassen [57] describes the CMC of some polyether carboxylates with different fatty chains and EO degrees (Fig. 2). In an extensive study, Binana-Limbele et al. [59] investigated the micellar properties of the alkylpolyether carboxylates of the general formula CnH + OCF CH OCI COONa with n = 8, x = 5, and n = 12 and x = 5,1, and 9, by means of electrical conductivity (CMC, apparent micellar ionization degree) and time-resolved fluorescence probing (micelle aggregation number A7) as a function of temperature and surfactant concentration (Table 1). 

Effective pH values in soft-core RMs. Characterization of the acidity in the aqueous soft-core is important as ionizable compounds are solubilized in the water pool. The micellar core has a very high degree of organization of water. The water pool within reverse micelles is a different solvent than bulk water. The most interesting range of water content corresponds to rather small water pools (water-to-surfactant ratio of 3 to 10) in which peculiar properties of water cause the largest changes in behavior as compared to their behavior in bulk water. A water to surfactant ratio of 1 1 represents a very small, almost undetectable, quantity of... 

An increase in the salt concentration leads to the progressive replacement of ions in the micellar corona by, e.g., ions of the added salt (i.e., increases the local pH in the corona). This promotes the increase in the degree of ionization a of the coronal blocks as ... 

At eqnifibrinm, the micelles have a net charge that is demonstrated by electrophoretic mobility experiments, for example, in an electric field, cationic micelles migrate toward a negative electrode. Typically, the surface charge at equilibrium is about 10-40% of the total number of micellized surfactant molecules. The net surface charge is numerically equal to the micellar degree of ionization (or ionization degree), a, which is experimentally obtained from the measured concentration of counterions to the aqueous pseudophase, [X ], corrected for the unimer concentration cmc, (5). A variety of methods may be used, for example, ion selective electrodes, conductivity NMR,... 

The degree of solubilization of weakly ionizing substrates, for example the substituted benzoic acids, is pH dependent and the solubilization data may be treated by a method proposed by Collett and Koo [73]. If the concentration of the solubilizate in the micellar and aqueous phases is denoted by Cm and Ca, respectively, and superscripts o and — used to denote unionized and ionized species, then the ratio R of the solubility in the surfactant to that in the aqueous phase is... 

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