Surfactant aggregation number

Surfactant solutions critical micelle concentration distribution of reactants among particles surfactant aggregation numbers interface properties and polarity dynamics of surfactant solutions partition coefficients phase transitions influence of additives... 

R Hansson and M. Akngren Interaction of Alkyltrimethylammonium Surfactants with Polyacrylate and Poly(Styrenesulfonate) in Aqueous Solution Phase Behavior and Surfactant Aggregation Numbers. Langmuir 10, 2115 (1994). 

Fig. 48 Surfactant aggregation numbers determined at various adsorption densities (average number at each adsorption density shown along the adsorption isotherm)...

Surfactant Aggregation number Micelles per mole (xlO-21) Hydrocortisone Dexamethasone Testosterone Progesterone... 

Hansson P, Almgren M. Interaction of alkyltrimethylammonium surfactants with poly(acrylate) and poly(styrenesulfonate) in aqueous solution. Phase behavior and surfactant aggregation numbers. Langmuir 1994 10 2115-2124. 

Hansson P, Almgren M. Interaction of C TAB with sodium(carboxymethyl) cellulose effect of polyion linear charge density on binding isotherms and surfactant aggregation number. J Phys Chem 1996 100 9038-9046. 

Table II displays the PLMA MW in the model system as a function of the alkyl chain length of the anionic surfactant, all other concentrations remaining constant. When the prepolymerization solution contains only C12EO5, the solution is opaque and the PLMA MW is large this result implies the existence of large micelles. Addition of sodium 2-ethylhexyl sulfate to the C12EO5-LMA prepolymerization solution at the concentration used for SDS (0.035 M) dramatically increases the MW. This result is presumably due to an electrolyte effect that increases nonionic surfactant aggregation numbers (3i), because the sodium 2-ethylhexyl sulfate concentration is far below the surfactant s CMC. However, doubling the sodium 2-ethylhexyl sulfate con-...

Thus, the situation is much more complex if the characteristics of the reverse micellar system (e.g., aggregation, micellar concentration, and dynamic behavior) are functions of time. In light of the available results, no definitive explanation can be offered at this time to account for the remarkable monodispersity obtained at intermediate R values, at which maximum number of nuclei is formed. Quantitative evaluation of the main features of the proposed model must await further experimental data. Of particular interest in this connection are the development of a quantitative description of the nuclei-aggregation process and the determination of surfactant aggregation numbers with water-ethanol mixtures as aqueous solubilizate. 

The elongation of the droplets may also effect a shift to the right of the monomer-droplet equilibrium of the surfactant [41]. Namely, the deviation from sphericity of a droplet with an aqueous pool of constant volume results in an increase of its water/oil interfacial area. The instability that results may be reduced by the entrance of surfactant monomers from the bulk phase, leading to an increase in surfactant aggregation number of the microemulsion particle in the presence of the field. 

To rationalize the above results, it is necessary to recall that changes in the water content result in significant changes in several properties of the microemulsion. Thus, with an increase in R, the surfactant aggregation number (TV), the concentration of free water, ... 

Since the determination of surfactant aggregation numbers and compartment sizes is based on the distinction between compartments occupied by both excited probe and quenchers from those occupied by only probe, a high quenching efficiency is required in such measurements. 

A. Surfactant Aggregation Numbers and Size of Closed Droplets... 

TABLE 1 Conductometricaily Estimated Water Pool Size Overall Droplet Dimension (R ), Surfactant Aggregation Number (A,), and Cosurfactant Aggregation Number (A,)per Droplet tor a Number of W O Microemulsions at 293 K at Constant Weight Fraction of Water = 0.2 and Surfactant Cosurfactant Weight Ratio = 0.5... 

To determine the onset of surfactant aggregation, necessary for the calculations of the surfactant aggregation numbers, cac was determined for 0.1% PEO at various NaCl concentrations by surface tension measurements using the drop-weight method. For this puipose, an apparatus built at the department s workshop was us. ... 

Figure 6. Surfactant aggregation numbers, , versus SDS/PEO-ratio.

Water, aqueous solutions and many other strongly hydrophilic substances can be solubilized within the micellar core [19,20], Water solubilization involves hydration of the surfactant headgroup accompanied by an increase in the head-group area, a micellar swelling, a marked increase in the surfactant aggregation number, and, at constant surfactant concentration, a decrease in the number density of reversed micelles [21], A representation of a spherical reverse micelle entrapping a polar solubilizate in the core is shown in Fig. 3. 

I/X2. Similar results were reported for the SDS/PVP sys-tem.2 2 These variations are probably related to the decrease of the surfactant aggregation number upon increasing polymer concentration and the corresponding changes in the micelle size distribution curve when the surfactant aggregates on the polymer.The submicellar aggregates at the minimrun of the distribution curve may be stabihzed when forming on the polymer. 

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