Surfactants - application and micelle formation

Surfactants are surface active agents which belong to a wide class of amphiphilic compounds [1, 2]. Surfactant molecules generally consist of a hydrophilic head of various nature (ionic or non-ionic) and a hydrophobic tail (a hydrocarbon chain), which is usually linear or branched. The surfactant concentration at which the association of a certain number of monomers leads to the formation of aggregates (micelles) is called the critical micelle concentration (CMC) [1]. To describe the micelle formation process the mass action model and the pseudo-phase separation model are generally applied. Micelles are thermodynamically stable forms. Aggregated structures (micelles) formed by surfactant molecules (monomers) in aqueous and non-aqueous solutions are shown in Figure 2. Surfactants and their micellar systems have immense technological applications. Surfactants are for example applied: in textile industry, in microelectronics for production of semiconductors, for production of mesoporous materials [25], in environmental research [26], as antiseptics [27], in cosmetic industry [1], as models of biological systems [28, 29, 32], for analysis of albumens [34], in pharmaceutical industry [1]. Sodium dodecyl sulfate (SDS ) and cetyltrimethylammonium bromide (CTAB ) are one of the most important surfactants in common use. In the last decade these surfactants were used: as ancillary means for removal of chemical pollutants from water [60], for preparation of cell electrodes [61], modification of nanoparticle size [62], modulation of fluorosensor activity [67, 70], activation of enzymes [71, 72], as stabilizers of drugs [73], in generation of chemical oscillators [74, 75], to induce changes in conformational behaviour of DNA molecules [10, 76–79]