MICELLIZATION THESIS SURFACTANT

Surfactants at an interface. In addition to the micelles shown in figure 3 so-called inverse micelles exist which cluster their head groups and orient their chains towards a surrounding non-polar phase. Moreover, varying parameters like temperature or system composition micelles can also adopt forms other than spherical, such as elongated and worm-like structures. Thus, for the correct determination of the cmc the partition of the dye has to be taken into account. We propose a model function for the monomeric and micellized surfactant concentration as function of the total surfactant concentration. This is achieved by the use of the concentration model eqs. The decrease of the interfacial tension caused by surfactants becomes stronger the more surfactants are adsorbed at the interface.

In liquid crystals also layered structures are found. Also the fluorescence emission of pyrene in micellar solutions fluorescence intensity, band ratio, excimer formation and fluorescence lifetimes are studied in detail. Surfactants are interfacially active compounds. Thus surfactants can mediate between two phases as they can form strong interactions with both of them. We have applied the concentration model eqs. Surface energy of a solid. We relate the finite width of the transition region below and above the cmc with the observed changes in the pyrene fluorescence in this region.

Concentration-model for surfactants near the cmc | QBFE -USC

We apply the model to the determination of the cmc from the pyrene fluorescence intensityespecially from the intensity ratio at two vibronic bands in the surfaactant emission or from the ratio of excimer to monomer emission intensity. The derived models are very useful tools for a consistent analysis of experimental data obtained from surfactant solutions with different techniques.

This is problematic, even for dyes with high affinity to micelles high values of K such as Pyrene, 2-anilinonaphthalenesulfonic acid ANS or different Coumarins.

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Moreover, varying parameters like temperature or system composition micelles can also adopt forms other than spherical, such as elongated and worm-like structures.

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It can be determined for surfactant solutions by measuring the surface tension at different concentrations. Thus, for the correct determination of the cmc the partition of the dye has to be taken into account. Concentration of monomeric surfactant [S 1 ]: Surface tension as a function of the surfactant concentration. Skip to main content. Thick curves are Global fits of the model equations to the data.

Fitting functions for specific properties of a surfactant solution can then be defined as a function of the monomeric and micellized surfactant concentration given by this concentration model.

Concentration-model for surfactants near the cmc

Please visit our blog for comments or questions or send us an email. We strongly recommend this fit of an objective model over the widely used graphical method based on the intersection of straight lines.

micellization thesis surfactant

Surfactants can be classified according to the charge of their polar head group:. See this page for examples of the curve fitting with the concentration model. Using the following buttons you can navigate between the individual chapters of our knowledge-base Understanding Interfaces.

Surfactants & critical micelle concentration (CMC) – DataPhysics Instruments

Schematic structure of a surfactant. The non-polar part, on the other hand, can form strong interactions with non-polar solvents, like oil, and is therefore also surfactnat lipophilic or hydrophobic part. An extrapolation of respective regression lines yields the CMC at the intersection. Dye exchange in micellar solutions. In liquid crystals also layered structures are found.

Surfactants & critical micelle concentration (CMC)

For example micelles form which consist of several clustered surfactant molecules that shield their non-polar chains from the surrounding aqueous phase with their polar head groups see figure 3. The concentration model for [S 1 ] and [S m ] eqs. Concentration of micelles [M]: The critical micelle concentration CMC is the surfactant concentration at and above which micelles are formed.

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The partition equilibrium constants K of the mentioned typical dyes are high but not infinite. We propose a model function for the monomeric and micellized surfactant concentration as function of the total surfactant concentration. Thus surfactants can mediate between two phases as they can form strong interactions with both of them. In a logarithmic representation of the surface tension versus the surfactant concentration there are two linear regimes below and above the CMC see figure 4.

Surfactants are interfacially active compounds. In addition to the micelles shown in figure 3 so-called inverse micelles exist which cluster their head groups and orient their chains towards a surrounding non-polar phase.

micellization thesis surfactant

The concentration model for [S1] and [Sm] eqs. The minimization of the unfavourable contact between non-polar surfactant chains and the polar solvent compensates the loss of entropy by micelle formation. Surfactants at an interface. Again, as in the case of the direct properties discussed above, the graphical determination of the cmc from straight lines does in general not give correct and reproducable results.

The absorption and fluorescence intensity of dyes in micellar solutions are micllization used for the determination of the cmc.