Penetration surfactant aggregates

The synergisms of mixtures of anionic-cationic surfactant systems can be used to form middle-phase micro emulsions without adding short-chain alcohols [109, 110]. The surfactants studied were sodium dihexyl sulphosuccinate and benzethonium chloride. The amount of sodium chloride required for the middle-phase microemulsion decreased dramatically as an equimolar anionic-cationic surfactant mixture was approached. Under optimum middle-phase microemulsion conditions, mixed anionic-cationic surfactant systems solubilised more oil than the anionic surfactant alone. Upadhyaya et al. [109] proposed a model for the interaction of branched-tail surfactants (Fig. 8.16). According to this model the anionic-cationic pair allows oil to penetrate between surfactant tails and increases the oil solubilisation capacity of the surfactant aggregate. Detergency studies were conducted to test the capacity of these mixed surfactant systems to remove oil from... 

The distribution constant for DTBA between or ary SDS micelles and water was determined to be 1800 M. The low value obtained when PEO is present, implies a substantial difference in the structure of the surfactant aggregate, even though the polymer does not penetrate the interior of the aggregate, but remains at the aggregate/water interface [9]. 

A full discussion of water penetration into micelles is beyond the scope of this chapter. The results described above, and others employing longer chain keto -surfactants in other micelles and bilayers, indicated a trend toward less water penetration to the core of aggregates as the surfactant tail length increased, and as aggregate curvature decreased (bilayer formation). More data from FT-IR studies... 

This micelle is comprised of surfactant molecules consisting of long hydrocarbon tails attached to an anionic lyophilic group. Typically, there are 50-100 molecules in the micelle. Some counterions in the medium are adsorbed on the aggregate, whereas others form the diffuse ionic environment. Some workers believe that there is considerable penetration of the medium into the micelle. Micelles are important for detergent action, with oily dirt particles dissolved in the hydrocarbon interior of the micelle. 

It can be seen that Eq. (2.157) is just the ordinary Langmuir equation in its generalised form (2.40) which follow rigorously from the analysis of chemical potentials of the components of a mixed monolayer. It was demonstrated that Pethica s equation provides the description of quite complicated systems, including the penetration of a soluble protein into the monolayer of insoluble phospholipids able to form 2D aggregates [155]. In another paper, the case of mixed layers composed of a soluble and a 2D aggregating insoluble surfactant is considered [156]. 

The case that the critical surface concentration Fic of the insoluble component depends on the adsorption of the soluble component, but, at the same time, the soluble surfactant does not form mixed aggregates and leads to an increase of the total adsorption of the monomers only, was discussed in [155, 157]. This situation exists when newly adsorbed (penetrated) molecules compensate the incorporation of free insoluble molecules into the condensed phase domains. 

The theory which describes the penetration of a soluble surfactant into a monolayer formed by molecules possessing equal partial molar area (mixtures of homologues), was extended recently to include the actual process of protein penetration into 2D aggregating phospholipid monolayer [155, 157]. This extension was based on the concept of independent segments of the protein molecules, occupying an area equal to that of the phospholipid molecule. In the theoretical models, various mechanisms for the effect of the soluble surfactant on the aggregation of the insoluble component can be considered ... 

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