Hydrophobicity, surfactants

Comparison of the second (IOS 2024) and last (linear IOS 2024) surfactants in Table 7 shows that the calcium ion tolerance of the linear hydrophobe surfactant is significantly greater than that of the partially branched hydrophobe surfactant. While branching was reduced substantially (33% to 6.6%) in going from IOS 2024 to linear IOS 2024, the hydrophobe carbon number and the disulfonate content of the surfactant were held constant. 

The common concentration of a surfactant used in a formulation varies from 0.05 to 0.5% and depends on the surfactant type and the solids content of the dispersion. In practice, very often combinations of surfactants rather than single agents are used to prepare and stabilize disperse systems. The combination of a more hydrophilic surfactant with a more hydrophobic surfactant leads to the formation of a complex film at the interface. A good example for such a surfactant pair is the Tween-Span system of Atlas-ICI [71]. 

Figure 4c shows that the amount of adsorbed proteins is rapidly saturated within several minutes of exposing serum-containing medium to a surface. Albumin, the most abundant serum protein, was expected to preferentially adsorb onto the surfaces during early time points. Then, adsorbed albumin was expected to be displaced by cell adhesion proteins. To investigate the effect of preadsorbed albumin displacement on cell adhesion, SAMs were first exposed to albumin then, HUVECs suspended in a serum-supplemented medium were added [21, 42]. Very few cells adhered to hydrophobic SAMs that had been pretreated with albumin, due to the large interfacial tension between water and the hydrophobic surfactant-like surface. Albumin was infrequently displaced by the cell adhesive proteins Fn and Vn. One the other hand, HUVECs adhered well to hydrophilic SAM surfaces that had been preadsorbed with albumin. In that case, the preadsorbed albumin was readily displaced by cell adhesive proteins. 

Uptake occurs from the bioavailable fraction, which in almost all cases corresponds to the dissolved fraction. Sorption and binding to suspended solids, sediments, and DOM have a great effect on bioavailability [71,72] therefore the more hydrophobic surfactants tend to be less bioavailable. Thus, for the same initial concentration, the bioavailable fraction of C12LAS, compared with that of the Cn... 

Johansson, J., Persson, P., Lowenadler, B., Roberston, B., Joemvall, H., and Curstedt, T. (1991). Canine hydrophobic surfactant plypeptide sp-c. A lipopeptide with one thioester-linked palmitoyl group. FEES Lett. 281, 119-122. 

Oosterlaken-Dijksterhuis MA, van Eijk M, van Golde LM, et al. Lipid mixing is mediated by the hydrophobic surfactant protein SP-B but not by SP-C. Bio-chim Biophys Acta 1992 1110(l) 45-50. 

In all of these data what requires explanation is the effectiveness of the dodecyl chain, the decreasing activity with increasing ethylene oxide chain length above EiQ-14 the increase in activity when we move from a very hydrophobic surfactant with short ethylene oxide chain to the optimum, and the decrease in activity with increasing lipophilicity of compounds with alkyl chain lengths greater than Cl2. 

Properties of surfactant and cosolvent additives affect the rate of apparent solubilization of organic contaminants in aqueous solutions and may serve as a tool in remediation of subsurface water polluted by NAPLs. Cosolvents (synthetic or natural) are organic solutes present in sufficient quantities in the subsurface water to render the aqueous phase more hydrophobic. Surfactants allow NAPLs to partition into the... 

These data demonstrate that more hydrophobic surfactants (lower HLB) are more effective as the situation in which they are initially exposed to the tar sand becomes less aqueous. In addition, this trend correlates with increased overall extraction. 

The use of alkylchlorosilanes as coupling agents for the synthesis of stable, hydrophobic, surfactant extracted MCM-48/VO, catalysts. 

Figure 3. Schematic representation of two different hexagonal arrangements in mesostructured inorganic / surfactant composites the hydrophobic chains are drawn as straight lines for simplicity, (a) The normal structure with a fully-connected inorganic network (dark area), (b) Inverse surfactant assemblies with single domains of the inorganic material enclosed in the centres. In the latter case the hydrophobic surfactant chains are allowed more space for their distribution, leading to a smaller d spacing. In this picture they are also interpenetrating each other.

Hydrophobic, Surfactant Extracted MCM-48/VOx Catalysts P. Van Der Voort and E.F. Vansant... 

Previous work has shown that binary surfactant systems containing Dowfax 8390 and the branched hydrophobic surfactant AOT can form Winsor III systems with both PCE and decane whereas DOWFAX 8390 by itself cannot (Wu et. al. 1999). This binary surfactant system was used in conjunction with hydrophobic octanoic acid to help with phase behavior and lessen the required concentration of CaCl2. Since this formulation is rather complicated, questions about field robustness arise. Thus, for the phase behavior studies presented here, we used the simple binary system of the nonionic TWEEN 80 and the branched hydrophobic AOT, and we optimized the NaCl concentration to give the Winsor Type III system. The lesser electrolyte concentration requirement for the binary TWEEN 80/ AOT system helps to decrease the potential for undesirable phase behavior such as surfactant precipitation, thereby increasing surfactant system robustness. 

The more hydrophobic surfactant system, AOT/TWEEN 80, exhibited the classical Winsor type I <=>III<=>II phase progression for diesel (Figure 4). This surfactant system also formed a middle phase containing equal volumes of hexadecane and water. At present it has not been determined if the classical Winsor Type I-III-II progression occurs for commercial motor oil (EACN = 22.3) with the AOT/Tween 80 system. 

The fingerprint region of the time - resolved spectra (Figure 27) also indicate the huge increase in C ECL at the C2g - water interface due to phase separation. Complete displacement of C26 by the phase of C12E03 does not occur. Thus, although penetration of this more hydrophobic surfactant can occur, a lack of involvement of water in the process results in poorer performance than can be accomplished at lower temperatures by the more hydrophilic C12E04. 

Calfactant is purified surfactant phospholipids extracted from calf lungs and purified by gel permeation chromatography. Calfactant include phospholipids, neutral lipides, and hydrophobic surfactant - three biophysically active proteins SP-A, SP-B, and SP-C. It contained no preservatives. 

Surfactants adsorb on solid surfaces due to hydrophobic bonding, electrostatic interaction, acid-base interaction, polarisation of rr electrons and dispersion forces. Hydrophobic bonding occurs between the hydrophobic surfactant tail and the hydrophobic solid surface (tail down adsorption with monolayer structure) or between the hydrophobic tails of the surfactant adsorbed on the hydrophilic solid surface and the hydrophobic tails of the surfactant from the liquid phase (head down adsorption with bilayer structure) [54, 55]. 

In a recent research, effect of hydrophobic surfactant proteins SP-B and SP-C on binary phospholipid monolayers was studied by IRRAS [65], The phospholipids examined were DPPC plus either DPPG or 1,2-dioleoyl-5 -glycero-3-phosphoglycerol (DOPG). IRRAS obtained at the air-water interface for a monolayer film of 7 1 DPPC-d62 DPPG plus 5 wt.% SP-B/C are shown in Fig. 5. Both C-H and C-D vibrational bands grow in intensity as the surface pressure increases and the surface density of the lipid molecules increases. As the average surface area per molecule is reduced, hydrophobic... 

Fig. 16. Schematic diagram illustrating the formation of a hydrophobic surfactant film on a polar surface. (After Franklin et al. [204].)...

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