Surfactants hydrophobic groups

As has already been mentioned, the effect of changes in the hydrophobic chain length on the effectiveness of surface tension reduction in nonionic surfactants is relatively minimal. Increases in the length of the polyoxyethylene chain, on the other hand, lead to significant reductions in the effectiveness of a given surfactant hydrophobic group. It appears, then, that the primary factor involved in the efficiency and effectiveness of nonionics in this application is the length of the... 

In highly diluted solutions the surfactants are monodispersed and are enriched by hydrophil-hydrophobe-oriented adsorption at the surface. If a certain concentration which is characteristic for each surfactant is exceeded, the surfactant molecules congregate to micelles. The inside of a micelle consists of hydrophobic groups whereas its surface consists of hydrophilic groups. Micelles are dynamic entities that are in equilibrium with their surrounded concentration. If the solution is diluted and remains under the characteristic concentration, micelles dissociate to single molecules. The concentration at which micelle formation starts is called critical micelle concentration (cmc). Its value is characteristic for each surfactant and depends on several parameters [189-191] ... 

The water structure at the water/surfactant interface depends on the nature of the surfactant head group, whereas the hydrophobic interface plays only a secondary role [91-93],... 

One of the most attractive roles of liquid liquid interfaces that we found in solvent extraction kinetics of metal ions is a catalytic effect. Shaking or stirring of the solvent extraction system generates a wide interfacial area or a large specific interfacial area defined as the interfacial area divided by a bulk phase volume. Metal extractants have a molecular structure which has both hydrophilic and hydrophobic groups. Therefore, they have a property of interfacial adsorptivity much like surfactant molecules. Adsorption of extractant at the liquid liquid interface can dramatically facilitate the interfacial com-plexation which has been exploited from our research. 

We will show several examples of the use of 2DLC for nonionic surfactants. The resulting resolution can be dramatically different depending on the two separation modes in the 2DLC system. As discussed previously, the separation of the hydrophobic groups can be accomplished with a reversed-phase column, and the separation of the... 

The hydrophobic group is usually a hydrocarbon chain and is generally called the tail, while the hydrophilic group, called the head, is an ionic group and very polar. Depending on the nature of the hydrophilic group, the surfactants are classified as ... 

Suitable collectors can render hydrophilic minerals such as silicas or hydroxides hydrophobic. An ideal collector is a substance that attaches with the help of a functional group to the solid (mineral) surface often by ligand exchange or electrostatic interaction, and exposes hydrophobic groups toward the water. Thus, amphi-patic substances (see Chapter 4.5), such as alkyl compounds with C to C18 chains are widely used with carboxylates, or amine polar heads. Surfactants that form hemicelles on the surface are also suitable. For sulfide minerals mercaptanes, monothiocarbonates and dithiophosphates are used as collectors. Xanthates or their oxidation products, dixanthogen (R - O - C - S -)2 are used as collectors for... 

Table III shows some data regarding the possible hydrophobic nature of ether sulfates. From several investigations, it is known that, for nonionic surfactants with identical hydrophobic groups, an increase in the hydrophilic part of the molecule causes a decrease in the aggregation number (28). This is caused by the...

During the past ten years, there have been numerous reports on the synthesis and the application of crown ethers of specific character to various fields. There have been also a few studies of the surface and micellar properties of crown ethers with hydrophobic groups (J - 17). The author has called them surface active crown ethers as a new class of surfactant possessing a promising function (11). 

Performance of surfactants is closely related to surface activity and to micelle formation. Both these are due to amphiphilic nature of the surfactant molecule. The molecule contains a nonpolar hydrophobic part, usually, a hydrocarbon chain, and a polar hydrophilic group, which may be nonionic, zwitterionic, or ionic. When the hydrophobic group is a long straight chain of hydrocarbon, the micelle has a small liquid like hydrocarbon core (1,2). The primary driving... 

It is important to consider the different stages when producing microemulsions from macroemulsions. It was mentioned earlier that surfactant molecules orient with the hydrophobic group inside the oil phase, while the polar group orients toward the water phase. The orientation of surfactants at the interfaces cannot be measured by any direct method, although much useful information can be obtained from mono-layer studies of the air-water or oil-water interfaces. 

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