Surfactant association

Exerowa and co-workers [201] suggest that surfactant association initiates black film formation the growth of a black film is discussed theoretically by de Gennes [202]. A characteristic of thin films important for foam stability, their permeability to gas, has been studied in some depth by Platikanov and co-workers [203, 204]. A review of the stability and permeability of amphiphile films is available [205]. 

Petroleum sulfonates are widely used as solubilizers, dispersants (qv), emulsifiers, and corrosion inhibitors (see Corrosion and corrosion inhibitors). More recentiy, they have emerged as the principal surfactant associated with expanding operations in enhanced oil recovery (66). Alkaline-earth salts of petroleum sulfonates are used in large volumes as additives in lubricating fluids for sludge dispersion, detergency, corrosion inhibition, and micellar solubilization of water. The chemistry and properties of petroleum sulfonates have been described (67,68). Principal U.S. manufacturers include Exxon and Shell, which produce natural petroleum sulfonates, and Pilot, which produces synthetics. 

In the simplest emulsions just described, the final separation is into two Hquid phases upon destabilization. The majority of emulsions are of this kind, but in some cases the emulsion is divided into more than two phases. One obvious reason for such a behavior is the presence of a material that does not dissolve in the oil or the water. One such case is the presence of soHd particles, which is common in emulsions for food, pharmaceuticals, and cosmetics. Another less trivial reason is that the surfactant associates with the water and/or the oil to form a colloidal stmcture that spontaneously separates from the two hquid phases. This colloidal stmcture may be an isotropic Hquid or may be a semisoHd phase, a Hquid crystal, with long-range order. 

Johansson, J., Szyperski, T, Curstedt, T., and Wuthrich, K. The NMR structure of the pulmonary surfactant-associated polypeptide SP-C in an apolar solvent contains a valyl-rich alpha-helix. Biochemistry 1994, 33, 6015-6023. 

Nonbiological methods for removal of trichloroethylene from water are also being studied. These include the use of a hollow fiber membrane contactor (Dr. A.K. Zander, Clarkson University), photocatalysis by solar or artificially irradiated semiconductor powders (Dr. G. Cooper, Photo-catalytics, Inc.), and micellar-enhanced ultrafiltration (Dr. B.L. Roberts, Surfactant Associates, Inc.). 

The role of various surfactant association structures such as micelles and lyotropic liquid crystals (372), adsorption-desorption kinetics at liquid-gas interfaces (373) and interfacial rheology (373) and capillary pressure (374) on foam lamellae stability has been studied. Microvisual studies in model porous media indicate... 

Surfactant molecules can be considered as building blocks for certain forms of geometry in colloidal chemistry. Various forms of association molecules can be obtained as the concentration of surfactant in water is increased and/or physicochemical conditions are changed (e.g. CMC, Craft-point, etc.). Figure 2 schematically shows the most likely structural configurations and assemblages of surfactants association in an aqueous system (26). Upon addition of oil and a short-chain alcohol, for example, one can convert the oil-in-water micelles into water-in-oil microemulsions. It is therefore possible to induce a transition from one structure to another by changing the physicochemical conditions such as temperature, pH and addition of mono or di-valent cations to the surfactant solution. It should be also noted that the sur-... 

Awareness of these environmental problems caused by surfactants, associated with their fate and toxicity, has led to a series of changes and... 

The sharp increase in adsorption in region II marks the onset of surfactant association at the surface through lateral interaction of the hydrocarbon chains. 

The decreasing slope in region III can be attributed to an increasing electrostatic hindrance to the surfactant association process following interfacial charge reversal. 

PSPD HUMAN P35247 PULMONARY SURFACTANT-ASSOCIATED PROTEIN... 

Balis JU, Bumgarner SD, Paciga JE, Paterson JF, Shelley SA (1984) Synthesis of lung surfactant-associated glycoproteins by A549 cells description of an in vitro model for human type II cell dysfunction. Exp Lung Res 6(3-4) 197-213... 

Patthy L. Homology of the precursor of pulmonary surfactant-associated protein SP-B with prosaposin and sulfated glycoprotein 1. J Biol Chem 1991 266(10) 6035-6037. 

Shiffer K, Hawgood S, Duzgunes N, et al. Interactions of the low molecular weight group of surfactant-associated proteins (SP 5-18) with pulmonary surfactant lipids. Biochemistry 1988 27(8) 2689-2695. 

In general we found that the oil solubilization rate is a function of the surfactant aggregate size. The maximum eff for a series of surfactant solutions seems to occur at the condition that the surfactant associates to the maximum aggregate volume without increasing the density of the aggregate. The eff value seems to parallel the final solubilization value of the surfactant. 

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... 

The surfactants associate at the oxide surface to form hemi-micelles with their hydrophobic groups exposed to the aqueous phase at low concentrations, but at higher concentrations, with the hydrophilic groups turned outwards. Hematite coated with various proteins (ovalbumin, y-globulin, lysozyme) adopted either the iep of the proteins or a value between that of the oxide and the protein and displayed modified coagulation behaviour (Johnson and Matijevic, 1992). 

T1he importance of association structures of amphiphilic molecules for interfacial phenomena has been realized in the last ten years with the rapid progress of knowledge concerning the structure of biomembranes and the discovery of the pronounced influence of surfactant association structures on the properties of disperse systems. 

Recently, an extensive study regarding a possible prediction of the association patterns of 1, 1-ionic surfactants in solvents with low dielectric constants has been proposed by Muller151,1S2. His model calculations are based upon a comparison between surfactant association patterns in solution and the formation of ionic lattices by (gaseous) alkali halides. The application of this latter process to the aggregation of detergent molecules in solution is certainly questionable with regard to many details, particularly, the considerations of internal rotational and vibrational entropic contributions in evaluating the stability of molecular clusters in solution. 

Figure 3.2S Surfactant associations in an O/W emulsion. The size of the surfactant molecules compared to the oil droplets has been greatly exaggerated for the purposes of illustration.

Now it is rather well established that ionic surfactants associate with cationic polyelectrolytes both in the bulk solution and at the interface. In our study it was found that the deformation increases after the SDS adsorption in the whole concentration range investigated. As can be seen from the Table 1, the SDS adsorption on practically non-deformed first adsorbed layer leads to the increase in f potential change value with pressure. 

In emulsion systems, an equilibrium between surfactant associated with the particles and free surfactant is considered to exist—i.e.,... 

Wennerstrom, H. Lindman, B. "Micelles, Physical Chemistry of Surfactant Association" Phys. Rep. 1979, 52, 1-86. 

Thus it is possible to estimate the time for surfactant adsorption required for the formation of black spots. Table 11.2 presents the clinical and threshold concentrations for total phospholipids (PL) and for disaturated phosphatidylcholine (DSPC) in each preparation. The most abundant PL of the lung surfactant system is DSPC, principally the DPPC species, which is believed the essential determinant of surfactant function in vivo [2], While DPPC is the only PL in EX, both IN and SU contain other PLs and small quantities of hydrophobic surfactant-associated proteins that may add to the desired functional properties of the material in situ. 

The surfactant association structures have a long history of research ranging from the McBaln introduction of the aqueous micellar concept(1.) over the interpretation of mlcelllzatlon as a critical phenomenon — — to the analysis of the structure of lyotropic liquid crystals(A) and the comprehensive picture of the phase relations in water/surfactant/amphlphile systems.These studies have emphasized the relation between the association structures in isotropic liquid solutions and the liquid crystalline phases. Parallel extensive investigations in crystalline/ liquid crystalline lipid structureshave provided important insight in the mechanisms of the associations. 

The result showing an increase of the minimum water concentration is directly understood from the association structures in the aqueous solution without electrolytes. The light-scattering determinations indicated that no surfactant association took place at low water concentrations for the system without electrolytes. An association structure of one surfactant molecule, a few associated water molecules, and one or two alcohol molecules is a reasonable conclusion. The experimental results showed no electrolyte solubility in the part of the solubility region where these non-associated structures were found for the electrolyte-free solution. A small structure containing only 10 water molecules cannot be expected to accommodate electrolytes and the structural analysis offers a satisfactory explanation of the results. 

If 10,000 cubic feet (10 Mcf) of CO2 costing 0.80/Mcf produce one barrel of oil, the CO2 cost is 8/bbl. Currently, CO2 utilization ratios of 10 Mcf/bbl are required for profitable operation (5). Thus, a surfactant-based process for improving sweep could cost as much as a few dollars per barrel of oil if it doubled the utilization ratio, and, correspondingly, smaller surfactant-associated costs would be commercially feasible for smaller improvements in the utilization ratio. 

Lesur O, Bernard AM, Begin RO. 1996. Clara cell protein (CC-16) and surfactant-associated protein A (SP-A) in asbestos-exposed workers. Chest 109 467-474. 

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