In amphoteric surfactants

Corresponding to the type of surfactant the hydrophobic group consists of an anion (anionics), a cation (cationics) or segment in nonionic or related polymer surfactants. Also, in amphoteric surfactants or betaine structures the fluorocarbon tail is extremely hydrophobic. 

Hidaka H, Nohara K, Pelizzetti E, Serpone N, Guillard C, Pichat P. Photooxidation processes in amphoteric surfactants catalyzed by irradiated Ti02 suspensions. J Adv Technol 1996 1 27-33. 

Methyl acrylate is a monomer used in the manufacture of plastic films, textiles, paper coatings, and other acrylate ester resins. It is also used in amphoteric surfactants. 

Rosenblatt, W., Amino acid amphoterics, in Amphoteric Surfactants, 2nd Edn, Lomax E. G. (Ed.), Surfactant Science Series 59, Marcel Dekker, New York (1996), pp. 49-73. 

Dimethylaminopropylamine is an aliphatic amine present in amphoteric surfactants such as liquid soaps and shampoos. It is present as an impurity responsible for allergy from cocamidopropylbetaine. It is structurally similar to diethylaminopropylamine. It is also used as a curing agent for epoxy resins and as an organic intermediate in chemical syntheses (ion exchangers, additives for flocculants, cosmetics and fuel additives, dyes and pesticides). 

Major industrial uses for chloroacetic acid are in the manufacture of cellulose ethers (mainly carboxymethylceUulose, CMC), herbicides, and thioglycolic acid. Other industrial uses include manufacture of glycine, amphoteric surfactants, and cyanoacetic acid. 

Anionic surfactants are the most commonly used class of surfactant. Anionic surfactants include sulfates such as sodium alkylsulfate and the homologous ethoxylated versions and sulfonates, eg, sodium alkylglycerol ether sulfonate and sodium cocoyl isethionate. Nonionic surfactants are commonly used at low levels ( 1 2%) to reduce soap scum formation of the product, especially in hard water. These nonionic surfactants are usually ethoxylated fatty materials, such as H0CH2CH20(CH2CH20) R. These are commonly based on triglycerides or fatty alcohols. Amphoteric surfactants, such as cocamidopropyl betaine and cocoamphoacetate, are more recent surfactants in the bar soap area and are typically used at low levels (<2%) as secondary surfactants. These materials can have a dramatic impact on both the lathering and mildness of products (26). 

Physical and ionic adsorption may be either monolayer or multilayer (12). Capillary stmctures in which the diameters of the capillaries are small, ie, one to two molecular diameters, exhibit a marked hysteresis effect on desorption. Sorbed surfactant solutes do not necessarily cover ah. of a sohd iaterface and their presence does not preclude adsorption of solvent molecules. The strength of surfactant sorption generally foUows the order cationic > anionic > nonionic. Surfaces to which this rule apphes include metals, glass, plastics, textiles (13), paper, and many minerals. The pH is an important modifying factor in the adsorption of all ionic surfactants but especially for amphoteric surfactants which are least soluble at their isoelectric point. The speed and degree of adsorption are increased by the presence of dissolved inorganic salts in surfactant solutions (14). 

Cationic, anionic, and amphoteric surfactants derive thek water solubiUty from thek ionic charge, whereas the nonionic hydrophile derives its water solubihty from highly polar terminal hydroxyl groups. Cationic surfactants perform well in polar substrates like styrenics and polyurethane. Examples of cationic surfactants ate quaternary ammonium chlorides, quaternary ammonium methosulfates, and quaternary ammonium nitrates (see QuARTERNARY AMMONIUM compounds). Anionic surfactants work well in PVC and styrenics. Examples of anionic surfactants ate fatty phosphate esters and alkyl sulfonates. 

Nonionic surfactants perform well in nonpolar polymers such as polyethylene and polypropylene. Examples of nonionic surfactants ate ethoxylated fatty amines, fatty diethanolamides, and mono- and diglycetides (see Amines, fatty amines Alkanolamines). Amphoteric surfactants find Httle use in plastics (134). 

An unknown commercial detergent may contain some combination of anionic, nonionic, cationic, and possibly amphoteric surfactants, inorganic builders and fillers as weU as some minor additives. In general, the analytical scheme iacludes separation of nonsurfactant and inorganic components from the total mixture, classification of the surfactants, separation of iadividual surfactants, and quantitative determination (131). 

Many of the surfactants made from ethyleneamines contain the imidazoline stmcture or are prepared through an imidazoline intermediate. Various 2-alkyl-imidazolines and their salts prepared mainly from EDA or monoethoxylated EDA are reported to have good foaming properties (292—295). Ethyleneamine-based imida zolines are also important intermediates for surfactants used in shampoos by virtue of their mildness and good foaming characteristics. 2- Alkyl imidazolines made from DETA or monoethoxylated EDA and fatty acids or their methyl esters are the principal commercial intermediates (296—298). They are converted into shampoo surfactants commonly by reaction with one or two moles of sodium chloroacetate to yield amphoteric surfactants (299—301). The ease with which the imidazoline intermediates are hydrolyzed leads to arnidoamine-type stmctures when these derivatives are prepared under aqueous alkaline conditions. However, reaction of the imidazoline under anhydrous conditions with acryflc acid [79-10-7] to make salt-free, amphoteric products, leaves the imidazoline stmcture essentially intact. Certain polyamine derivatives also function as water-in-oil or od-in-water emulsifiers. These include the products of a reaction between DETA, TETA, or TEPA and fatty acids (302) or oxidized hydrocarbon wax (303). The amidoamine made from lauric acid [143-07-7] and DETA mono- and bis(2-ethylhexyl) phosphate is a very effective water-in-od emulsifier (304). 

Protease performance is strongly influenced by detergent pH and ionic strength. Surfactants influence both protease performance and stabiUty in the wash solution. In general, anionic surfactants are more aggressive than amphoteric surfactants, which again are more aggressive than nonionic surfactants. 

Amphoteric surfactants are those that are an acid and a base at the same time (like water is). Cocamidopropyl betaine, for example, is used in shampoos to stabilize foam and thicken the mixture. 

Whereas amphoteric surfactants are somewhat outside the scope of this book, amphoteric LSDAs are included here since they were investigated in the course of continuing research by the USDA team. Thus Parris and coworkers found that the sulfobetaine derivatives of fatty amides, in combination with soap, effectively dispersed soap curd [20]. They are synthesized as follows ... 

Blends of surfactants optimized for seawater or reservoir brine salinity include linear alkylxylene sulfonate/alcohol ether sulfate mixtures (454,455). Alkyl- and alkylarylalkoxymethylene phosphonates (456), and amphoteric surfactants (457,458) have also been evaluated for use in surfactant flooding. 

As mentioned in Table 8.1, amphoteric surfactants contain both an anionic and a cationic group. In acidic media they tend to behave as cationic agents and in alkaline media as anionic agents. Somewhere between these extremes lies what is known as the isoelectric point (not necessarily, or even commonly, at pH 7), at which the anionic and cationic properties are counterbalanced. At this point the molecule is said to be zwitterionic and its surfactant properties and solubility tend to be at their lowest. These products have acquired a degree of importance as auxiliaries in certain ways [20-25], particularly as levelling agents in the application of reactive dyes to wool. 

Ethoxylated products can also feature as amphoteric surfactants an example is compound 9.55, an alkylamine poly(oxyethylene) sulphate. Of particular interest in textile processing are the trisubstituted alkylamino acids known as betaines N-alkylbetaines (9.56 R = C8-C16 alkyl) and acylaminoalkylbetaines (9.57 R = C10-C16 alkyl) are typical [30]. 

A surfactant can be grouped in one of the four classes - anionic, nonionic, cationic and amphoteric surfactants, depending on what charge is present in the chain-carrying hydrophilic portion of the molecule after dissociation in aqueous solution. Tab. 4.1 shows examples of surfactants most commonly used for detergents. 

Contrary to anionic and nonionic agents, they have poor detergency and are used more in the preparation of germicides, fabric softeners, and emulsifiers. Amphoteric surfactants are produced in much smaller amounts (5xl04 metric tons, near to 2% of the total production) [125] they are biodegradable and their ecotoxicological importance can be considered low. Their environmental occurrence up to know has been just occasional. 

High polarity is one of the reasons why both the ionic and amphoteric surfactants, and especially their metabolites, are difficult to detect. This property, however, is important for the application tasks of surface-active compounds, but is also the reason for their high water solubility. Due to this fact, their extraction and concentration from the water phase, which can be carried out in a number of very different ways, is not always straightforward. Furthermore, they are often not volatile without decomposition, which thus prevents application of gas chromatographic (GC) separation techniques combined with appropriate detection. This very effective separation method in environmental analysis is thus applicable only for short-chain surfactants and their metabolites following derivatisation of the various polar groups in order to improve their volatility. 

The two distinctive affinities in the surfactant molecule mentioned above serve as the basis for the commonly accepted definition of surfactant groups. According to the charge of their hydrophilic moiety, surfactants can be classified into four categories anionic, non-ionic, cationic and amphoteric. 

Amphoteric surfactants have two or more functional groups which, depending on the conditions of the medium, can be ionised in aqueous solutions to give the compound the characteristics of either an anionic... 

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