Exchange between surfactant

Rharbi, Y, Winnik, M.A. Solute exchange between surfactant micelles by micelle fragmentation and fusion. Adv. Colloid Interface Sci. 2001, 89-90, 25-46. 

The structure of these globular aggregates is characterized by a micellar core formed by the hydrophilic heads of the surfactant molecules and a surrounding hydrophobic layer constituted by their opportunely arranged alkyl chains whereas their dynamics are characterized by conformational motions of heads and alkyl chains, frequent exchange of surfactant monomers between bulk solvent and micelle, and structural collapse of the aggregate leading to its dissolution, and vice versa [2-7]. 

The situation is similar to the exchange between the monomer and the micellar states. Usually, the exchange between the monomer and the micellar states is fast. The spectra at surfactant concentrations above CMC, therefore, consist of a single set of peaks whose chemical shifts are averaged between the monomer and micellar states. Such an example is shown by spherical micelles formed by lithium perfluoro-octylsulfonate (FOS )... 

Clays-pillared clays or organoclays 2D, 3D varies Purification and ion exchange by surfactants of naturally occurring products or synthesis Weeks to months Interlayer distance could be varied and precisely determined X-ray diffraction measurements particles could be grown in situ or incorporated between layers complex supramolecular architecture was possible 478,480,482... 

The surfactant used in this study is decyltrimethylammonium bromide (DTAB). It was chosen because it has the longest hydrocarbon chain length for which the fast monomer exchange between the micelle and bulk phases can be monitored by ultrasonic techniques. 

The environment of the surfactant molecules undergoes a marked change when they associate together to form micelles. The chemical shifts of certain nuclei of the surfactant molecules in the micellar state will consequently become different from those in the molecular dispersed state. It is well known that the exchange between the molecules of the two states in the solution is fast, so the observed chemical shift is the weighted value of the two species according to the following expression ... 

Figure 4. Adsorption of cationic surfactant, BDDAB, and its polar head, BTAB, onto precipitated silica at 298 K (a) cation exchange between solute ions and sodium counterions upon adsorption (b) electrophoretic mobility of silica particles against amount adsorbed.

If the surface of an equilibrium surfactant solution is disturbed (expanded, compressed, renewed, etc.), the system will try to restore the equilibrium by exchange of surfactant between the surface and the subsurface layer (adsorption-desorption). The change of the surfactant concentration in the subsurface layer triggers a diffusion flux in the solution. In other words, the process of equilibration (relaxation) of an expanded adsorption monolayer involves two consecutive stages ... 

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