Role of surfactants

Flow of trains of surfactant-laden gas bubbles through capillaries is an important ingredient of foam transport in porous media. To understand the role of surfactants in bubble flow, we present a regular perturbation expansion in large adsorption rates within the low capillary-number, singular perturbation hydrodynamic theory of Bretherton. Upon addition of soluble surfactant to the continuous liquid phase, the pressure drop across the bubble increases with the elasticity number while the deposited thin film thickness decreases slightly with the elasticity number. Both pressure drop and thin film thickness retain their 2/3 power dependence on the capillary number found by Bretherton for surfactant-free bubbles. Comparison of the proposed theory to available and new experimental... 

Mizukoshi Y, Takagi E, Okuno H, Oshima R, Maeda Y, Nagata Y (2001) Preparation of platinum nanoparticles by sonochemical reduction of the Pt(IV) ions role of surfactants. Ultrason Sonochem 8 1-6... 

Vandivier, R.W., et al., Role of surfactant proteins A, D, and Clq in the clearance of apoptotic cells in vivo and in vitro Calreticulin and CD91 as a common collectin receptor complex, J. Immunol. 169, 7, 3978, 2002. 

Bogman K, Erne-Brand F, Alsenz J, Drewe J (2003) The role of surfactants in the reversal of active transport mediated by multidrug resistance proteins. J Pharm Sci 92 1250-1261. 

As discussed before (4) it is perhaps convenient to classify these theories into three main categories interfacial or mixed film theories, solubilisation theories and thermodynamic theories. Below a brief description of each of these classes will be given with particular emphasis on the role of surfactant nature and structure. 

Polymer/Surfactant Interactions. Interaction between polymers and surfactants was recently reviewed by Robb (11) and surfactant association with proteins by Steinhardt and Reynolds (12). Polymer/surfactant interactions are highly dependent on the chemical nature of the polymer and the surfactant. In general, surfactants tend to associate with uncharged polymers in aggregates rather than individual surfactant molecules interacting with the macro-molecule. The ability of surfactants to form micelles is thought to be an important factor in the role of surfactant behavior in interactions with polymers. Individual surfactant... 

Stevens, P.J.G., Baker. E.A., and Anderson. N.H. Factors affecting the foliar absorption and redistribution of pesticides. 2. Physicochemical properties of the active ingredient and the role of surfactant, Pestic. Sci., 24(l) 31-53,1988. 

S. Brdsel and H. Schubert Investigation of the Role of Surfactants in Mechanical Emulsification Using a High-Pressure Homogenizer with an Orifice Valve. Chem. Eng. Process. 38, 533 (1999). 

The role of surfactant molecules in the synthesis of Fe-Zn DMC is probably to increase the surface area and add sites density, thereby enhancing the catalytic... 

It is generally accepted that one of the attractive features of the microemulsion environment for materials synthesis is the stabilization of the produced particles by the microemulsion surfactants. However, in the specific case of alkoxide/ microemulsion systems, there have been no investigations into the manner in which this stabilization is effected. For example, when the particle size exceeds the microemulsion droplet size, are the particles expelled from the water pools, or do the particles rather induce the enlargement of the microemulsion water droplets There have been no investigations into the role of surfactant adsorption in the colloidal... 

Role of Surfactant Film in Restricting Particle Growth... 

Strano MS, Moore VC, Miller MK, Allen MJ, Haroz EH, Kittrell C, Hauge RH, Smalley RE. The role of surfactant adsorption during ultrasonication in the dispersion of single-walled carhon nanotubes. Journal of Nanoscience and Nanotechnology 2003, 3, 81-86. 

Physicochemical properties of the active ingredient and the role of surfactant. Pestic. Sci. 24, 31-53. 

Surfactants play a major role in the preparation of suspensions of polymer particles by heterogeneous nucleation. In emulsion polymerization, the monomer is emulsified in a nonsolvent (usually water) using a surfactant, whereas the initiator is dissolved in the continuous phase. The role of surfactants in this process is obvious since nucleation may occur in the swollen surfactant micelle. Indeed, the number of particles formed and their size depend on the nature of surfactant and its concentration (which determines the number of micelles formed). 

The role of surfactants in stabilization/destabilization of foam (air/liquid dispersions) is similar to that for emulsions. This is due to the fact that foam stability/instability is determined by the surface forces operative in liquid films between air bubbles. In many industrial applications, it is essential to stabilize foams against collapse, e.g., with many food products, foam in beer, fire-fighting foam, and polyurethane foams that are used for furniture and insulation. In other applications, it is essential to have an effective way of breaking the foam, e.g., in distillation... 

Additives are usually amphiphilic in nature, and thus are either ionic or neutral surfactants or even polymers. The role of surfactants in solvent extraction is ambiguous. Usually, they should be avoided as they lower the interfacial tension, which may lead to emulsion formation in an agitated extractor. However, every metal-loaded ion exchanger is amphiphilic, and can adsorb at the interface or aggregate in the bulk phase. This occurrence is well known with sodium or other metals [17], and above a critical surfactant concentration (cmc, critical micelle concentration) micellar aggregates are formed. A dimensionless geometric parameter is decisive for the structure of the associates, according to Fig. 10.6 ... 

The Role of Surfactants in Modifying the Activity of Herbicidal Sprays... 

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