Physicochemical studies of surfactant systems in presence and absence of additives

Abstract

A surfactant is a surface active amphiphile that aggregates (self assembles) in water or other solvents to form various microstructures such as micelles or bilayers. The amphiphile with more or less equilibrated hydrophilic and lipophilic tendencies are likely to migrate to surfaces or interfaces. Amphiphiles often exhibit other properties besides lowering of surface tension. Because of its split personality, an amphiphilic molecule doesn t feel at ease in any solvent. newlineMicelles are aggregates of amphiphiles above a certain minimum concentration in a solution known as critical micelle concentration (CMC). McBain1 and Hartley,2 from their preliminary research work, had concluded that micelles are spherical (or roughly spherical) in shape and since then a large number of reports have surfaced out. The formation of micelles in aqueous solution is viewed as a compromise between the tendency for the alkyl chains to avoid energetically unfavorable contacts with water, and a desire for the polar parts to maintain contact with the aqueous environment. The biological amphiphilic molecules aggregate into spherical and nonspherical clusters (vesicles), and thus biomembranes share features with these colloidal systems. The unusual properties of aqueous surfactant solutions can be ascribed to the presence of a hydrophilic head group and a hydrophobic chain in the molecule. The polar or ionic head groups usually interact strongly with an aqueous environment, in which case it is solvated via dipole dipole interactions. It is the nature of the head group, which is used to divide surfactants into different categories as cationic, anionic, nonionic, and zwitterionic.Surfactans exhibit a fascinating range of applications in almost every chemical industry, such as in detergents, floatation, paints, dyestuffs, paper coatings, inks, plastics, fibers, personal care and cosmsetics, agrochemicals, pharmaceuticals, food processing, etc. They also play a vital role in the oil industry (e.g., in enhanced tertiary oil recovery), oil slick