Surface-active agents surfactants compounds

Micelles are molecular aggregates formed in solutions of surface-active agents (surfactants compounds that orient at an interface such as between oil and water) (McAulifFe, 1980). Micelles may contain up to 100 or more surfactant molecules with a nonpolar (hydrophobic) end on the inside and a polar (hydrophilic) end on the outside. In 1959, Baker first advanced the concept of solubilization of hydrocarbons in (soap) micelles as a possible primary migration mechanism. The possible role of soaps, i.e. salts of organic acids, in primary migration was supported by Cordell (1973). The concept was considered attractive because it also explains how the practically water-insoluble hydrocarbons can solubilize in groundwater at relatively low temperatures. However, the likelihood of micellar solution as an effective primary migration mechanism has been seriously questioned by many authors (for instance Price, 1976 Hunt, 1979 Tissot and Welte, 1984). The main problems associated with micellar solution are ... 

Enhancement of the aqueous solubility by surfactants occurs as a result of the dual nature of the surfactant molecule. The term surfactant is derived from the concept of a surface-active agent. Surfactants typically contain discrete hydrophobic and hydrophilic regions, which allow them to orient at polar-nonpolar interfaces, such as water/air interfaces. Once the interface is saturated, th surfactants self-associate to form micelles and other aggregates, whereby their hydrophobic region are minimized and shielded from aqueous contact by their hydrophilic regions. This creates a discrete hydrophobic environment suitable forsolubilization of many hydrophobic compounds (Attwood and Florence, 1983 Li et al., 1999 Zhao et al., 1999). 

Surfactant — A widely used contraction of surface active agent, a compound that alters surface tension of a liquid in which it is dissolved. 

The word "surfactant" is a widely used contraction of "surface-active agent," a compound that alters the surface tension of a liquid in which it is dissolved (1). Surfactants impart stability to polymers during the foaming process. They help control cell structure by regulating the size, and to a large degree, the uniformity of the cells. In urethane foams the choice of surfactant is governed by factors such as polyol type and method of foam preparation (13). 

Surface-active agent. (surfactant). Any compound that reduces surface tension when dissolved in water or water solutions, or that reduces interfacial tension between two liquids, or between a liquid and a solid. There are three categories of surface-active agents detergents, wetting agents, and emulsifiers all use the same basic chemical mechanism and differ chiefly in the nature of the surfaces involved. 

To prevent cissing, an additive that reduces interfacial tension is required in the paint. When interfacial tension falls, the particle is wetted by the finish and absorbed into the film. Surface-active agents Surfactants, see below) reduce interfacial tension. Alternatively, an agent can be added that will reduce the liquid surface tension so much, that the interfacial tension also becomes low. Silicone oils do this effectively. Very little silicone oil is required, because it finds its way almost entirely to the surface. Silicones are semi-organic compounds... 

Surface-active agents (surfactants) are a series of compounds consisting of hydrophobic and hydrophilic moieties. An aqueous solution containing a surfactant forms micelles above a critical concentration, which is called the critical micelle concentration (cmc). The value of the cmc is approximately (1 M = 1 moldm ) in the case of... 

The structural requirements for a surfactant in an organic liquid are quite different from the structures of typical fluorinated surfactants used in water. In order to function as a surface-active agent, a compound has to be amphiphilic and consist of lyophobic (solvent insoluble) and lyophilic (solvent soluble) groups in the molecule [86]. In water, the hydrophobic group of the surfactant causes a re-... 

Surface-Active Agents. Polyol (eg, glycerol, sorbitol, sucrose, and propylene glycol) or poly(ethylene oxide) esters of long-chain fatty acids are nonionic surfactants (qv) used in foods, pharmaceuticals, cosmetics, textiles, cleaning compounds, and many other appHcations (103,104). Those that are most widely used are included in Table 3. 

A great number of nonionic surfactants have been ethoxylated and subsequently reacted with P4O10. The acid phosphate esters from this reaction possess surface properties and detergency similar to the nonionic surface-active agents employed as reactants. Detergency tests and foam heights from the Ross-Miles method have been reported for a series of compounds. Various formulations for all-purpose cleaners are given as well [37,40,41,44,48]. 

The inhibition of Streptococcus mutans adherence to hydroxyapatite with combinations of alkyl phosphates and nonionic surfactants was tested. Seven alkyl phosphate derivatives and three nonionic surfactants were examined for their ability to inhibit the adherence of 3H-labeled cells of S. mutans to hydroxyapatite treated with buffer or parotid saliva. No compound by itself effectively hindered binding of bacteria to hydroxyapatite. A combination of certain of the alkyl phosphates, notably a disodium phosphate of 1-octadecanol, and nonionic surfactant at a 1 1 molar ratio gave a strong inhibition of S. mutans adherence. Treatment with this combination resulted in 98% reduction of adherence. Adsorption of the two types of surface-active agents alone and in combinations was studied using 14C-labeled agents. Electrophoretic measure-... 

Modem commercial detergents are mixtures. Their most important component is a surfactant, or surface-active agent, which takes the place of the soap. Surfactant molecules are organic compounds with a structure and action similar to those of soap. A difference is that they typically contain sulfur atoms in their polar groups (4). 

Surface active agents, more commonly known as surfactants, are the groups of chemical compounds that in the most common form constitute an ionic or polar portion (hydrophilic head) and a hydrocarbon portion (hydrophobic tail). The ionic or polar portion interacts strongly with the water via dipole-dipole or ion-dipole interactions and... 

To increase the usefulness of bioremediation as an effective field remedial tool, significant investments have been made towards the development of means to remove sorbed PAHs, attack sources of NAPL, and subsequently increase the aqueous solubility/bioavailability, and thus the biodegradability, of targeted compounds. To date, one of the most effective ways to accomplish these tasks involves the use of surface active agents (i.e., surfactants). A variety of synthetic surfactants have been shown effective in increasing the bioavailability of PAHs and other hydrophobic contaminants (Kile Chiou, 1989, 1990 Edwards et al., 1991 Liu et al., 1991). Although the solubilization process is not completely understood, these studies showed that a variety of ionic and nonionic surfactants could significantly increase the water solubility of monitored chemicals. 

The essential ingredients of all these hair and skin products are part of a broad class of compounds called surfactants, which is short for "surface active agents "All surfactant molecules are polar on one end and nonpolar on the other. Because of their nonpolar ends, they resist dissolving in water and instead cling to water s surface where their nonpolar ends stick up out of the water. Pour some oil onto the surfactant containing water and the nonpolar tails will cling to the oil s surface. In this way, surfactants bind together the surfaces of water and a nonpolar material. 

As expected, the influence of added nonelectrolytes can be quite different depending on whether the added compound is likely to be located in the micelles or in the in-termicellar solution. The effect of normal alcohols has been studied in detail for potassium dodecanoate the CMC is lowered for all alcohols studied but the effect increases considerably in going from ethanol to decanol (cf. Fig. 2.7). Hydrocarbons, like cyclohexane, n-heptane, toluene, and benzene, have been found to lower the CMC for many surfactants. Strongly hydrophilic substances, like dioxane and urea, have small and complex effects. At higher concentrations they markedly increase the CMC or even inhibit micelle formation. Addition of another similar surface-active agent generally gives a CMC in between the CMCs of the two surfactants. 

Crystallization from the emulsified state may lead to different nucleation processes than observed for the same fat in bulk liquid form. It has been suggested that nucleation often occurs at the interface of the droplet where surface-active agents are located. The general similarity of the lipophilic components of surfactants oriented at the surface may provide some ordering and structure for the lipid molecules within the droplet and enhance nucleation, as found for example by Kaneko et al. (40) for a hydrocarbon emulsion. Walstra (11) also suggests that formation of compound crystals from emulsions of natural fats may be different than the same fat crystallized from bulk liquid. The initial polymorph formed may also be different, with more stable polymorphs more likely to form in the emulsion (38). 

Certain compounds, because of their chemical structure, have a tendency to accumulate at the boundary between two phases. Such compounds are termed amphiphiles, surface-active agents, or surfactants. The adsorption at the various interfaces between solids, liquids and gases results in changes in the nature of the interface which are of considerable importance in pharmacy. For example, the lowering of the interfacial tension between oil and water phases facilitates emulsion formation the adsorption of surfactants on the insoluble particles enables these particles to be dispersed in the form of a suspension and the incorporation of insoluble compounds within micelles of the surfactant can lead to the production of clear solutions. 

It is difficult to remove dirt from skin or clothing using only water. Because dirt particles cannot penetrate the surface of the water drops, the water cannot remove the dirt. What happened when you added a drop of detergent to the heaker in the DISCOVERY LAB Soaps and detergents decrease the surface tension of water hy disruphng the hydrogen bonds between water molecules. When the bonds are broken, the water spreads out. Compounds that lower the surface tension of water are called surface active agents or surfactants. 

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