Relationship between surfactant

Somasundaran, P., R. Middleton, and K. V. Viswanathan, Relationship between surfactant structure and adsorption . In Structure/Performance Relationship in Surfactants, M. J. Rosen, Ed., American Chemical Society, Washington, DC, 1984, pp. 269-290. 

The majority of the bioconcentration data is based on experiments with radiolabelled surfactants. Since the measurements of radioactivity were performed without prior separation of metabolites, the data are not specific for the parent surfactants and therefore not a quantitative measure of surfactant bioconcentration (Tolls et al., 1994). The general trend observed in these data is that bioconcentration of surfactant increases with decreasing values of the CMC, indicating that a relationship between surfactant bioconcentration and hydrophobicity exists (Tolls and Sijm, 1995). This trend has been confirmed with parent compound-specific data measured for LAS (Tolls et al., 1997). 

A preferred location of the solubilizate molecule within the micelle is largely dictated by chemical structure. However, solubilized systems are dynamic and the location of molecules within the micelle changes rapidly with time. Solubilization in surfactant aqueous systems above the critical micelle concentration offers one pathway for the formulation of poorly soluble drugs. From a quantitative point of view, the solubilization process above the CMC may be considered to involve a simple partition phenomenon between an aqueous and a micellar phase. Thus the relationship between surfactant concentration Cm and drug solubility Ctot is given by Eq. (3). 

Baldauf LM, Schechter RS, Wade WH, Graciaa A. The relationship between surfactant phase behavior and the creaming and coalescence of macroemulsions. J Colloid Interface Sci 1982 85 187-197. 

Synthetic surfactants and the natural fatty acid soaps are amphiphihc materials that tend to exhibit some solubility in water as well as some affinity for nonaqueous solvents. As a basis for understanding the relationship between surfactant structures and surface activity, it is useful to work through the simple example of how changes in the polarity (ie, the head group) for a specified hydrocarbon chain affects its solubility and surface activity. As an illustration, consider the simple, straight-chain hydrocarbon dodecane. 

For now, the discussion will be limited to some general concepts related to adsorption at liquid-fluid interfaces, such as some general relationships between surfactant structure and the rate and effect of adsorption. 

Of particular interest is the case of surfactant adsorption onto surfaces of opposite charge, in which a complex relationship between surfactant concentration and wetting is often encountered (Fig. 17.13). At low surfactant concen-... 

A detailed discussion was presented on the relationship between surfactant adsorption and the solid surface charge. For the anionic surfactant, as expected, as the surface became increasingly positive the adsorption increased. This increase in positive charge occurred either when the rock type was changed in the order shown above while keeping the brine fixed or when divalent cations were added to the brine for a fixed rock type. 

Fig. 3 a Relationship between surfactant accumulated on the interface and the structural viscosity of the creams (water content 80 w/w /o, D=10s ). b Relationship between contact angle of wetting and the structural viscosity of the creams (water content 80 w/... 

Complexation has frequently been correlated with the hydrophobic character of one (or both) of the interacting ions [273-279]. Details of the interaction between a series of dyes and alkyltrimethylammonium bromides have been published [277], The structure of the dyes used, tartrazine (XXVI) amaranth (XXVII) carmoisine (XXVIII) and erythrosine (XXIX) are shown below. These are all important colours used in the food, drug and cosmetic industries. Phase separation diagrams were constructed to indicate the relationship between surfactant concentration and the anisotropic solution-coacervate boundary. Differences between the interactions of a hydrophilic dye, tartrazine and amaranth, carmoisine and erythrosine which have both hydrophobic and hydrophilic moieties were exhibited. Tartrazine appears to behave like a simple electrolyte interacting simply with the charged groups at the micellar surfaces while the other dyes complexed and were solubilized as a complex in addition to interacting with the micelle surface [277]. These dyes also induced the formation... 

It is because of the dependence of HLB on the solution properties of the surfactant molecules that HLB numbers cannot always be realistic measurements of actual HLB, which will depend on the nature of the solvent, the temperature and presence or absence of additives. The relationship between surfactant CMC... 

Figure 1. Relationship between surfactant concentration and HOC solubility.

Detailed HCB solubility studies were performed with three surfactants (Tween 60, Tween 80 and Triton X-100) to provide for a range in surfactant properties and biological compatibility. In the absence of surfactant, the solubility of HCB at 25°C was found to be approximately 7 jiig/L, which is similar to values reported in the literature (75). Relationships between surfactant concentration and the apparent solubility of HCB are shown in Figure 5. Interestingly, the aqueous-phase concentration of HCB increased by approximately one-order-of-magnitude as the CMC of each surfactant was approached. Similar trends were reported by Kile and Chiou (7), who observed an increase in the apparent solubility of DDT from 5.5 jug/Lin pure water to approximately 70-80 /ig/L at the CMC of three Triton series surfactants. This behavior is attributed to interactions between the dissolved HOC and the hydrophobic moiety of surfactant monomers. 

The relationship between surfactants and particle size of the emulsion is of paramount importance. In general, increasing surfactant level decreases particle size. However, the relationship is an exponential one, and each surfactant type has a maximum level above which the particle size does not decrease. 

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