Phase transfer using amphiphilic molecules

The terminology of L-B films originates from the names of two scientists who invented the technique of film preparation, which transfers the monolayer or multilayers from the water-air interface onto a solid substrate. The key of the L-B technique is to use the amphiphih molecule insoluble in water, with one end hydrophilic and the other hydrophobic. When a drop of a dilute solution containing the amphiphilic molecules is spread on the water-air interface, the hydrophilic end of the amphiphile is preferentially immersed in the water and the hydrophobic end remains in the air. After the evaporation of solvent, the solution leaves a monolayer of amphiphilic molecules in the form of two-dimensional gas due to relatively large spacing between the molecules (see Fig. 15 (a)). At this stage, a barrier moves and compresses the molecules on the water-air interface, and as a result the intermolecular distance decreases and the surface pressure increases. As the compression from the barrier proceeds, two successive phase transitions of the monolayer can be observed. First a transition from the gas" to the liquid state. 

Nonionic surfactants are one of the most important and largest surfactant groups. They are amphiphilic molecules composed, in most cases, of poly(ethylene oxide) (PEO) blocks as the water-soluble fragment and fatty alcohols, fatty acids, alkylated phenol derivatives, or various synthetic polymers as the hydrophobic part [1], This class of surfactants is widely used as surface wetting agents, emulsifiers, detergents, phase-transfer agents, and solubilizers for diverse industrial and biomedical applications [2],... 

Ammonium salts are well-known cationic surfactants. These amphiphilic molecules aggregate in aqueous solution to micelles and at higher concentrations to lyotropic (typical member is CTAB, eetyltimethylammonium bromide) (or thermotropie) mesophases. Beside this ammonium salts are used as phase transfer catalysts and as ionic liquids (ILs) in synthesis of nanopartickle catalysts [70-74],... 

Due to their amphiphilic structure, the PEHO-based PILs represent effective phase transfer agents for transportation of hydrophilic molecules into non-polar media.A series of experiments, where PILs with an outer shell of n-butyl, -dodecyl, and -octadecyl substituents were used for transferring the water-soluble dye Congo red from an aqueous phase into chloroform, demonstrated the transport efficacy of the PILs. After... 

While PTC does not involve solubilization or micellar catalysis in the sense discussed above and seldom involves what are generally considered to be surfactants, it does require the use of catalysts that are amphiphilic in nature. Its basic mechanism, as described below, also brings up some potentially interesting questions related to interfaces, the activity of amphiphilic molecules in multiphase systems, and the transport of ionic species from one phase to the other across such interfaces. Because of those loose, but interesting connections between micellar catalysis and phase transfer catalysis, the following introduction to the theme has been included. 

Irreversible transfer reactions have been used in the past to generate block copolymers from hydrophilic or amphiphilic thiol molecules such as sodium 10-mercapto-1 -decanesulfonate [99], or functionalized PEO [100] or poly(VAc-ct)-vinyl alcohol) [101]. In fact, the very efficient transferring nature of the thiol function leads to a high reactivity of the transurf in the dispersing phase. Although the in situ formation... 

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