Surfactants schematic representation

Figure 6.10 Schematic representation of the distribution of surfactant in an emulsion polymerization. Note the relative sizes of suspended particles. [From J. W. Vanderhoff, E. B. Bradford, H. L. Tarkowski, J. B. Shaffer, and R. M. Wiley,Chem. 34 32(1962).]...

The conformational dynamics of chain segments near the head groups is more restricted than that of those far from the micellar core [8]. Moreover, to avoid the presence of energetically unfavorable void space in the micellar aggregate and as a consequence of the intermolecular interactions, surfactant molecules tend to assume some preferential conformations and a staggered position with respect to the micellar core [9]. A schematic representation of a reversed micelle is shown in Figure 1. 

Fig. 10.14 Schematic representation of the membrane = 47 mm), mesostructured silica-synthetic route to dynamic functionalized me- surfactant before (B) and after (C) calcination, sostructured silica membranes in the AAMs ODS-hydrophobized silica before (D) and after...

Finally, we have designed and synthesized a series of block copolymer surfactants for C02 applications. It was anticipated that these materials would self-assemble in a C02 continuous phase to form micelles with a C02-phobic core and a C02-philic corona. For example, fluorocarbon-hydrocarbon block copolymers of PFOA and PS were synthesized utilizing controlled free radical methods [104]. Small angle neutron scattering studies have demonstrated that block copolymers of this type do indeed self-assemble in solution to form multimolecular micelles [117]. Figure 5 depicts a schematic representation of the micelles formed by these amphiphilic diblock copolymers in C02. Another block copolymer which has proven useful in the stabilization of colloidal particles is the siloxane based stabilizer PS-fr-PDMS [118,119]. Chemical... 

Figure 5.46 Schematic representation of helical and twisted ribbons as discussed in Ref. 165. Top Platelet or flat ribbon. Helical ribbons (helix A), precursors of tubules, feature inner and outer faces. Twisted ribbons (helix B), formed by some gemini surfactant tartrate complexes, have equally curved faces and C2 symmetry axis. Bottom Consequences of cylindrical and saddlelike curvatures in multilayered structures. In stack of cylindrical sheets, contact area from one layer to next varies. This is not the case for saddlelike curvature, which is thus favored when the layers are coordinated. Reprinted with permission from Ref. 165. Copyright 1999 by Macmillan Magazines.

Figure 8. (A) Schematic representation of the shape of the function f(rt). The arrows represent the first order like phase transition effect. The two straight lines are f(tt) = 17.5tt + 20.0 and f(n) = O.Olrc, respectively. (B) Schematic representation of the relationship between the surface pressure (ji) and the effective concentration of surfactant at the air/water interface (T f). The solid and dashed lines represent the expected and ideal relationships, respectively.

Fig Schematic representation of surfactant molecules distributed in water (A) completely dissolved at low concentration and... 

Numerous books and reviews have been published on this subject (e.g. Fendler and Fendler, 1975 Mittal, 1977). Therefore, the structural characteristics of micelles will be presented only to the extent that is necessary for the subsequent discussions. These surfactants form micelles at concentrations above the cmc (critical micelle concentration). Such micelles have average radii of 12-30 A and contain 20-100 surfactant molecules. The hydrophobic part of the aggregate forms the core of the micelle while the polar head groups are located at the micellar surface. Micelles at concentrations close to their cmc are assumed to possess spherical and ellipsoidal structures (Tanford, 1973, 1978). A schematic representation of a spherical ionic micelle is shown in Fig. 1. 

Figure 12.1 Schematic representation of a micelle (bottom) by aggregation of cetyltrimethylammonium bromide (C H NfCHUiBr-) surfactant molecules (top)...

Rgure 1.6. (a) Schematic formulation-composition map. SAD is the surfactant affinity difference it is positive for a lipophilic surfactant and negative for a hydrophilic one. The gray zones are abnormal, (b) Schematic representation of the proposed mechanism for a transitional inversion, (c) Schematic representation of the proposed mechanism for a catastrophic phase inversion. 

Figure 2 Schematic representation of the linear and semi-branched architectures of two non-ionic polymeric surfactants...

Fig. 23 Schematic representation of the formation of polymer surfactant complexes for the pyrene-labeled (polyacrylic acid)-dodecyltrimethylammonium bromide system for high (high pH) and low (low pH) degrees of ionization...

The settling rate of the dispersions in cyclohexane initially increases with AOT adsorption but later decreases. The initial increase is attributed to the formation of interparticle surfactant aggregates (Fig. 39A). At higher concentrations, the adsorbed molecules aggregate with excess of surfactant in solution rather than with molecules on the particle, so that flocculation ceases to occur and the dispersion is restabilized. The schematic representation of the surfactant assemblies at the interface is as shown in Fig. 39B. 

Fig. 2 Schematic representation of some organized structures formed using surfactants...

In order to be exploitable for extraction and purification of proteins/enzymes, RMs should exhibit two characteristic features. First, they should be capable of solubilizing proteins selectively. This protein uptake is referred to as forward extraction. Second, they should be able to release these proteins into aqueous phase so that a quantitative recovery of the purified protein can be obtained, which is referred to as back extraction. A schematic representation of protein solubilization in RMs from aqueous phase is shown in Fig. 2. In a number of recent publications, extraction and purification of proteins (both forward and back extraction) has been demonstrated using various reverse micellar systems [44,46-48]. In Table 2, exclusively various enzymes/proteins that are extracted using RMs as well as the stability and conformational studies of various enzymes in RMs are summarized. The studies revealed that the extraction process is generally controlled by various factors such as concentration and type of surfactant, pH and ionic strength of the aqueous phase, concentration and type of CO-surfactants, salts, charge of the protein, temperature, water content, size and shape of reverse micelles, etc. By manipulating these parameters selective sepa-... 

Figure 9.9 Schematic representation of aqueous and reverse micelles (cross sections), with the structure of the most popular surfactant for reverse micelles, the AOT i.e., bis(2-ethylhexyl)sodium sulfosuccinate. The typical conditions to obtain reverse micelles are as follows isooctane, 25-1000 mM AOT, 0.2-2% water, ITo = [H20]/[A0T].

Fig. 62. A schematic representation of the hydrostatic-pressure-induced bending of a BLM. Distribution of DPH (indicated by ) in the BLMs should only be considered to be schematic. In reality, the ratio of surfactants DPH was 1 300 [412]...

FIGURE 11.4 Schematic representation of a water-in-oil-in-water emulsion. The gray represents the water phase, where the protein or poly(nucleic acid) would be present. The black dots surrounding the white oil phase represents a surfactant, typically poly(vinyl alcohol) or serum albumin. 

Figure 4 (A) A spherical reversed micelle of a negatively charged micro droplet of water stabilised by cationic surfactant molecules. (B) Schematic representation of the steric interactions in the reversed micelle which favors the formation of linear alkyl rhodium intermediates.

Table 6.2 Schematic representation of nanoscale structure and experimental data relating to self-assembly of sodium caseinate induced by interactions of the protein (1.0 % w/v) with micelles of food-grade surfactants (CITREM and SSL) in an aqueous medium (pH = 5.5, ionic strength = 0.05 M, 293 K) above the surfactant cmc. 

FIG. 8.8 Schematic representations of surfactant structures in (a) viscous isotropic, (b) middle, and (c) neat liquid crystal phases. 

Figure 3. Schematic representation of the structure of M0S-L-I6C with the surfactant cations interdigitated (left) and being in the form of double layers (right) between the sulfide layers.

According to the results shown here, we may conclude that the composition of these nanoribbons is related to a composite formed by the association of the smallest LDH particles (perhaps crystallites, as shown by AFM) and the surfactant. These adsorbed LDH particles may be oriented in the c axis, and linked by the adsorbed surfactant layer and surfactant molecules. A schematic representation of such composite is shown in Figure 7. 

Figure 7. Simplified schematic representation of the composition and formation process of the LDH-surfactant composite, according to the proposed model.

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.

Figure 23. (a) Schematic representation of an anionic surfactant azobenzene derivative monolayer film at the air-water interface. (i>) Schematic representation of the stable monolayer film formed from the polyion complex of anionic surfactant azobenzene derivatives with a cationic polymer. Note the difference in free volume around the reactant chromophores in the two monolayers. 

Figure 8.3. Schematic representation of the relationship between the phase behavior and interfacial tension for water/C02/ionic surfactant mixtures as a function of formulation variables.

Figure 2.32.1 Schematic representation of the structural features of the various anionic surfactants.

Figure 4.39 Schematic representations of the various types of electrode surfaces for which protein voltammetry is commonly observed (a) a metal electrode modified with an XY SAM (b) a metal oxide electrode (c) an electrode modified with a surfactant layer in which protein molecules are embedded (d) a pyrolitic graphite edge electrode, often used in conjunction with mobile co-adsorbates such as aminocyclitols. Reprinted from Uectrochim. Acta, 45, F.A. Armstrong and G.S. Wilson, Recent developments in faradaic bioelectrochemistry, 2623-2645, Copyright (2000), with permission from Elsevier Science...

Fig. 4 Schematic representation of lamellar—.hexagonal phase transformation (a through d) and the hexagonal—reubic transformation (e and f). The shaded circles around the surfactant aggregates represent the inorganic species (generally metal alkoxides or other metal-oxo species).

Fig. 3.11. Folding of T4 DNA by the addition of the gemini surfactant. Distributions of the long-axis length of T4 DNA at different concentrations [cs] of the surfactant. Coil, partially folded, and completely folded states are distinguished by the different colorings. Also shown are FM and AFM images with the corresponding schematic representation of the partially folded state ([cs] =0.2 pM) and completely folded state ([cs] = 1.0pM). The FM and AFM observations are of the same DNA molecules attached to a mica surface. A rings-on-a-string structure is clearly seen for the partially folded DNA, while the completely folded DNA assumes a network structure composed of many fused rings (see [19] for more details)...

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