Surfactants and Self-assembly

Introduction to the variety of types of surfactants, effect of surfactants on aqueous solution properties. Law of mass action applied to the self-assembly of surfactant molecules in water. Spontaneous self-assembly of surfactants in aqueous media. Formation of micelles, vesicles and lamellar structures. Critical packing parameter. Detergency. Laboratory project on determining the charge of a micelle. 

The name surfactant refers to molecules that are surface-active , usually in aqueous solutions. Surface-active molecules adsorb strongly at the water-air interface and, because of this, they substantially reduce its surface energy (Gibbs theorem). This is the opposite behaviour from that observed for most inorganic electrolytes, which are desorbed at the air interface and hence raise the surface energy of water (slightly). Surfactant molecules are amphiphilic, that is, they have both hydrophilic and hydrophobic moieties, and it is for this reason that they adsorb so effectively at interfaces (note that amphi means of both kinds in Greek). 

Applied Colloid and Surface Chemistry Richard M. Pashley and Marilyn R Karaman 2004 John Wiley Sons, Ltd. ISBN 0 470 86882 1 (HB) 0 470 86883 X (PB) 

A list of typical surfactant molecules, with different types of charge, is given in Table 4.1. 

In addition to the surface adsorption properties of surfactants, they also have the remarkable ability to self-assemble in aqueous solution. The structures spontaneously formed by surfactants in solution are created 

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Bio-Interfacial Engineering Coating Process Fundamentals Polymer Microstructures Surfactancy and Self-Assembly... 

The chemistry involved in the formation of mesoporous silica thin films is qualitatively well understood. However, specific reaction mechanisms of the individual steps are still debated. In addition, owing to the complexity of the sol-gel reaction pathways and cooperative self-assembly, full kinetic models have not been developed. From the time of mixing, hydrolysis reactions, condensation reactions, protonation and deprotonation, dynamic exchange with solution nucleophiles, complexation with solution ions and surfactants, and self-assembly, all occur in parallel and are discussed here. Although the sol-gel reactions involved may be acid or base catalyzed, mesoporous silica film formation is carried out under acidic conditions, as silica species are metastable and the relative rates of hydrolysis and condensation reactions lead to interconnected structures as opposed to the stable sols produced at higher pH. Silicon alkoxides are the primary silica source (tetramethyl orthosilicate, tetraethyl orthosilicate, tetrapropyl orthosilicate, etc.) and are abbreviated TMOS, TEOS, and TPOS, respectively. Starting from the alkoxide, Si(OR)4, in ROH and H2O solution, some of the general reactions are ... 

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