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Surfactants double-tailed

Cationic surfactants may be used [94] and the effect of salinity and valence of electrolyte on charged systems has been investigated [95-98]. The phospholipid lecithin can also produce microemulsions when combined with an alcohol cosolvent [99]. Microemulsions formed with a double-tailed surfactant such as Aerosol OT (AOT) do not require a cosurfactant for stability (see, for instance. Refs. 100, 101). Morphological hysteresis has been observed in the inversion process and the formation of stable mixtures of microemulsion indicated [102]. [Pg.517]

While most vesicles are formed from double-tail amphiphiles such as lipids, they can also be made from some single chain fatty acids [73], surfactant-cosurfactant mixtures [71], and bola (two-headed) amphiphiles [74]. In addition to the more common spherical shells, tubular vesicles have been observed in DMPC-alcohol mixtures [70]. Polymerizable lipids allow photo- or chemical polymerization that can sometimes stabilize the vesicle [65] however, the structural change in the bilayer on polymerization can cause giant vesicles to bud into smaller shells [76]. Multivesicular liposomes are collections of hundreds of bilayer enclosed water-filled compartments that are suitable for localized drug delivery [77]. The structures of these water-in-water vesicles resemble those of foams (see Section XIV-7) with the polyhedral structure persisting down to molecular dimensions as shown in Fig. XV-11. [Pg.549]

This range yields more highly tmncated cones. The main mesophase stmcture obtained from these units is a flexible bilayer such as that fonned in vesicles and liposomes. These arrangements are often obtained from doublechain surfactants such as lecithin, double tailed cationic surfactants and AOT. [Pg.2588]

The idealized reverse micelle sketched in figure C2.3.1 is an aggregate of a double-tail surfactant. In such systems the solvent is more compatible with the lyophobic part of the surfactant than with the headgroup. This preference... [Pg.2590]

When anionic and cationic surfactants are mixed they strongly interact, and it could even be said that they almost react to produce a catanionic species, which is essentially a new surfactant, in which the two hydrophilic groups have merged into a nonionic or a somehow amphoteric head attached to a double tail. The first consequence is that the new daughter species has... [Pg.103]

Figure 5.2 Top-diagramatic representation of a detergent molecule, (a) Single tailed (b) double tailed (c) zwitterionic (d) bolamphiphilic. Bottom - different types of surfactant aggregates in solution (A) monolayer (B) bilayer (C) liquid-crystallin phase lamellar (D) normal micelles (E) cylindrical micelles (hexagonal) (F) vesicles (liposomes) (G) reversed micelles. Figure 5.2 Top-diagramatic representation of a detergent molecule, (a) Single tailed (b) double tailed (c) zwitterionic (d) bolamphiphilic. Bottom - different types of surfactant aggregates in solution (A) monolayer (B) bilayer (C) liquid-crystallin phase lamellar (D) normal micelles (E) cylindrical micelles (hexagonal) (F) vesicles (liposomes) (G) reversed micelles.
Why do biological membranes and bilayers usually consist of double-tailed surfactants ... [Pg.399]

Generally, vesicles are prepared from double-tailed surfactants, and a simple single-tailed surfactant cannot form vesicles due to its relatively large hy-... [Pg.323]

Cubic strut phases are common in the phase diagrams of two-tailed surfactants. These surfactants have a relatively high value of the vfaolc parameter, because the volume-to-length ratio v/i(. of the double tail is twice that of a single tail. A high value of v/aoic is consistent with the formation of type II bicontinuous and other inverse phases, such as the inverse hexagonal phase in Fig. 12-24. [Pg.582]

Figure 29 Vesicles made of the double-tailed surfactant (33) and containing in the internal water pool the quinolinium derivative (35) are destroyed by acetylcholinesterase, very probably leading to the formation of micelles made of (34) and n-hexadecanol. In the process, (35) is also released and cleaved by the enzyme [98]... Figure 29 Vesicles made of the double-tailed surfactant (33) and containing in the internal water pool the quinolinium derivative (35) are destroyed by acetylcholinesterase, very probably leading to the formation of micelles made of (34) and n-hexadecanol. In the process, (35) is also released and cleaved by the enzyme [98]...
Hirasaki et al. (2008) demonstrated an alternative to the use of alcohol by blending two dissimilar surfactants a branched alkoxylated sulfate and a double-tailed, internal olefin sulfonate. The presence of cosolvent affects the effective salinity and causes a shift in phase boundaries. Alcohol is an organic compound with a functional group of -OH. In aqueous solutions, the hydrogen can become detached, producing slightly acidic solutions. Alcohols with short... [Pg.277]

The controlled introduction of two lipophilic alkyl chains into mannuronate monomers represents a convenient way of producing double-tailed surfactants (Scheme 6). Indeed, the incorporation of longer hydrophobic alkyl chains than the two butyl groups brings a more amphiphilic character to the glycosides. [Pg.153]

Double-tailed ester-type surfactants 6a-c, f, g and uronamides 10c, f, g were studied as to their properties as emulsifying agents. Three systems were studied sunflower oil-water, paraffin oil (Marcol 82)-water, and capric/caprylic triglycerides (Oleon)-water. In order to determine the w/o or o/w type of emulsions formed in the presence of the surfactants, the drop-dilution method was used. To a small portion of the emulsicMi (surfactant/water/oil 5/47.5/47.5 in weight) placed oti a slide, a drop of water with a pin point is added and stirred slightly. If the water blends with the emulsion, it is an oil-in-water emulsion, but if oil blends with the outside phase it is a water-in-oil emulsion. As indicated in Table 5, ester-type and amide-type compounds 6a-c and 10c, based on C8 to C12 fatty alcohols and amines, are able to form o/w emulsions whereas surfactants 6f, g and lOf, g composed of stearic (Cl8) or oleic (C18 l) alkyl chains exhibit w/o emulsions. [Pg.161]


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See also in sourсe #XX -- [ Pg.153 ]




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