Hydrophilic structure zwitterionic surfactants

Surface active substances or surfactants are amphiphilic compounds having a lyophilic, in particular hydrophilic, part (polar group) and a lyophobic, in particular hydrophobic, part (often hydrocarbon chain). The amphiphilic structure of surfactants is responsible for their tendency to concentrate at interfaces and to aggregate in solutions into various supramolecular structures, such as micelles and bilayers. According to the nature of the polar group, surfactants can be classified into nonionics and ionic, which may be of anionic, cationic, and amphoteric or zwitterionic nature. 

AFM imaging has been used to identify interfacial aggregate structure above the cmc for a variety of ionic, nonionic, and zwitterionic surfactants on both hydrophobic and hydrophilic surfaces. (Structures far below the cmc, corresponding to the low-density adsorption plateau, cannot be imaged readily because the tip-sample force is strongly hydrophobic and attractive in this regime.) The... 

The discontinuous cubic phase is, without exception (so far as is known), the solubility boundary that exists just above the Krafft eutectic in zwitterionic surfactants. This phase is also the saturating phase at the solubility boundary in many quaternary ammonium salts (such as dodecyltrimethylammonium chloride). It is also prominent in polyfunctional quaternary ammonium surfactants such as dodecyl-tris(2-hydroxyethyl)ammonium chloride [23]. It is interesting that the cubic liquid-crystal solubility boundary is not often found when lipophilic proximate substituent groups do not exist on or near the primary hydrophilic group, as in alkylammonium chlorides (RNH3, Cl ). In contrast, structurally... 

Structure Formation in Surfactant Solutions. Surfactants, also referred to as soaps, detergents, tensides, or surface active agents, are amphiphilic molecules possessing both hydrophilic and hydrophobic regions. They can be classified as anionic, cationic, zwitterionic, or nonionic (neutral) depending upon the nature of the polar... 

Surfactants have been used for over 1000 years in everyday applications, for example as emulsifiers in cleaning and in foods. They occur widely in nature, where as a bilayer they constitute a vital structural unit of biological membranes. Their functionality derives from the molecular structure, with a polar (hydrophilic) head-group, which conveys water-solubility, being attached to a non-polar (hydrophobic) tail, which drives the formation of self-assembled aggregates (micelles). Other chapters in this volume detail the wide variety of chemical structures that can form the polar groups (ionic, nonionic, zwitterionic, etc.) and tail structures. 

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