Surfactants ampholytic

Ampholytic surfactants based on phosphatides, betaines and alky lamino-substituted amino adds are an increasingly important group of surfactants and are generally reported to be reasonably biodegradable. 

As discussed before, there are two regions (i.e., hydrophilic and hydrophobic) in the surfactant molecules. These surfactants are classified into four main categories depending on the nature of the charge carried by the hydrophilic part of the surfactant anionic, cationic, nonionic, and ampholytic surfactants. Some common examples of surfactants are listed in Table 4.4. 

Ampholytic surfactants possess both cationic and anionic groups in the same molecule and are dependent on the pH of the medium. Lecithin is used for parenteral emulsions. 

Makhmudov, T. -M, Khidoyatov, K. K and Khakimov, A. S., Synthesis, properly study, and development of technology for making ampholyte surfactants based on aromatic hydroxy acids, in Tr. 7ili Mezhdunar, Kongr. Poverkhn Akl Veshchestvam, 1976 Chem. Abstr., 91,59211, 1979. 

Ampholytic surfactants (also called zwitterio-nic surfactants), where the molecule contains, or can potentially contain, both a negative and a positive charge, (e.g., the sulfobetaines, RN" "(CH3)2CH2CH2S03 ). Examples of pharmaceutical importance include V-Dodecyl-V, V-Dimethylbetaine, Ci2H25N+(CH3)2CH2COO. ... 

The zwitterionic or ampholytic surfactants shown in Box 6.1 possess both positively and negatively charged groups and can exist as either an anionic or a cationic surfactant depending on the pH of the solution. A typical example is N-dodecyl-N,N-dimethylbetaine (Ci2H25N"(CH3)2CH2COO). 

Properties Cl. yel. liq. sol. in water misc. with anionic, nonionic, and ampholytic surfactants, fatty acid alkanolamidesi dens. dens. 1.045-1.055 vise. 400-600 mPa.s pH 6.5-7.0 26-28% solids... 

Cottrell was the first who used a PVC-coated wire electrode for the determination of low concentrations of surfactants. Extensive articles and excellent overviews on CWEs for the determination of surfactants were published by Vytras s group, who were very active in developing simple coated wire electrodes for cationic and ampholytic surfactants especially during the... 

Amphoteric Detergents. These surfactants, also known as ampholytics, have both cationic and anionic charged groups ki thek composition. The cationic groups are usually amino or quaternary forms while the anionic sites consist of carboxylates, sulfates, or sulfonates. Amphoterics have compatibihty with anionics, nonionics, and cationics. The pH of the surfactant solution determines the charge exhibited by the amphoteric under alkaline conditions it behaves anionically while ki an acidic condition it has a cationic behavior. Most amphoterics are derivatives of imidazoline or betaine. Sodium lauroamphoacetate [68647-44-9] has been recommended for use ki non-eye stinging shampoos (12). Combkiations of amphoterics with cationics have provided the basis for conditioning shampoos (13). 

Amphiphile-oil-water system, temperature of, 16 424-426 Amphiphiles, 16 420 Amphiphile strength, 6 424 Amphiphilic chemicals, 17 56 Amphiphilic copolymers, 20 482 behavior of, 20 483 well-defined, 20 485-490 Amphiphilic molecules, 15 99-101 Amphiphilic plasticizers, 14 480 Amphiphilic polymer blend, 23 720 Amphiphilic polymers statistical, 20 484-490 stimuli-responsive, 20 482-483 Ampholytes, 9 746-747 Amphoteric cyclocopolymers, water-soluble, 23 721 Amphoteric starches, 4 722 Amphoteric (zwitterionic) surfactants, 24 148... 

Surfactants in broad use may be classified into three general types (I) anionics, in which the hydrophilic portion of the molecule carries a negative charge (2) cationics. in which the charge of this portion is positive and (3) nonionics, which do not dissociate but commonly derive their hydrophilic portion from polyhydroxy or polyelhoxy structures. Ampholytic and it itlerionic surfactants are also known and arc starting to be of commercial importance. 

Depending on their chemical structure, surfactants capable of forming micelles are usually classified into cationic e.g. ammonium salts), anionic e.g. sulfates, carboxylates), ampholytic e.g. zwitterionic salts), and non-ionic surfactants (usually containing polyoxyethene chains) cf. Table 2-10 in Section 2.5. 

The currently favoured working hypothesis for the stabilization mechanism of the particles is to claim an ampholytic surface structure, whereas the cationic surfactant only stabilizes the hydrophobic "patches" of the non-ionic methylsilane group, the remaining surface of the particles is stabilized by the anionic Si-0 groups. 

Ampholyt [H lsAG] Glycinates betaines amphoteric surfactant for cosmetics, shampoos, detergents. 

At or in the proximity of their pi values proteins exhibit a minimum total charge and reduced solubility in the electrolyte solution [350,370,385]. This increases the probability of aggregation, and is further enhanced by the low ionic strength of the ampholyte buffer. Under these conditions protein precipitation results from hydrophobic interactions. These interactions can be suppressed by addition of additives such as ethylene glycol (10-40 %), non-ionic or zwitterionic surfactants (1-4 %), or sorbitol to the ampholyte buffer. 

Zwitterionic surfactants have positive and negative charges on the head group. Amphoteric surfactants have a head group with a pH-dependent charge. The amine oxide shown in Fig. 3 is zwitterionic at high pH, but becomes cationic as protonation occurs at low pH. Because amphoteric surfactants are generally zwitterionic at some pH. and zwitterionic surfactants are often amphoteric, in practice, the terms zwitterionic and amphoteric are used as synonyms, and the term ampholytic is used to describe both surfactant types. 

With respect to the properties of polar groups, surfactants can be subdivided into ionic (cation- and anion-active, ampholytic, and zwitterionic) and nonionic surfactants. If the effect produced by the polar group of the surfactant molecule is more significant than that of the lipophilic group, this substance is soluble in water. It is less surface active as compared to any substance characterized by an optimum balance between the activities of hydrophilic and lipophilic groups. Similar conclusions can be drawn also with respect to the solubility in oil here, the role of the lipophilic group is determining. Clearly, the efficiency of a surfactant is not determined solely by the amphiphilicity, but depends on the hydrophilic/lipophilic balance (HLB) characteristic for this compound. Therefore, this balance is an important characteristic of both the surfactant and the interface. 

Anionic surfactants are little used in breweries while cationic surfactants such as quaternary ammonium compounds are employed for certain biocidal applications. Ampholytic (amphoteric) surfactants are also used as biocides and like the quaternary ammonium compounds they have to be rigorously... 

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