Amphiphilic components

Tb clarify the effect of addition of a cationic HC surfactant on phase separation behavior in the mixed monolayers of anionic HC and FC surfactants polyion complexed with cationic polymers, the mixed monolayers containing three amphiphilic components complexed with PVA were transferred on various substrate plates and studied by AFM, FFM, SSPM, and SIMS. As a cationic surfactant, ODTMAC was examined. 

Kaznessis et al. [24] used Monte Carlo simulations on a data set of 85 molecules collected from various sources, to calculate physically significant descriptors such as solvent accessible surface area (SASA), solute dipole, number of hydrogen-bond acceptors (HBAC) and donors (HBDN), molecular volume (MVOL), and the hydrophilic, hydrophobic, and amphiphilic components of SASA and related them with BBB permeability using the MLR method. After removing nine strong outliers, the following relationship was developed (Eq. 37) ... 

The term microemulsion is applied in a wide sense to different types of liquid liquid systems. In this chapter, it refers to a liquid-liquid dispersion of droplets in the size range of about 10-200 nm that is both thermodynamically stable and optically isotropic. Thus, despite being two phase systems, microemulsions look like single phases to the naked eye. There are two types of microemulsions oil in water (O/W) and water in oil (W/O). The simplest system consists of oil, water, and an amphiphilic component that aggregates in either phase, or in both, entrapping the other phase to form... 

Deamer, D. W. and Pashley, R. M. (1989). Amphiphilic components of the Murchison carbonaceous chondrite surface properties and membrane formation. Orig. Life Evol. Biosph., 19, 21-38. 

Earlier reports [50] showed that vesicles composed of oleic acid can grow and reproduce as oleoyl anhydride spontaneously hydrolyzed in the reaction mixture, thereby adding additional amphiphilic components (oleic acid) to the vesicle membranes. This approach has recently been extended by Hanczyc et al. [51], who prepared myristoleic acid membranes under defined conditions of pH, temperature, and ionic strength. The process by which the vesicles formed from micellar solutions required several hours, apparently with a rate-limiting step related to the assembly of nuclei of bilayer structures. However, if a mineral surface in the form of clay particles was present, the surface in some way catalyzed vesicle formation, reducing the time required from hours to a few minutes. The clay particles were spontaneously encapsulated in the vesicles. The authors further found that RNA bound to the clay was encapsulated as well. 

As previously mentioned, the functionalization of the external surface of liposomes was achieved through the preparation of mixed liposomes. In this manner, the functional moieties at the external surface originate from the amphiphilic components, which were incorporated in these mixed liposomes. It was thus possible to monitor the reactivity of liposomes by changing the type and concentration of the incorporated recognizable lipid. 

The main difference between the lipid samples under investigation is their lipid class composition (Table 1). The unreacted CLO contains nearly only TG while the main difference between Residue A and B was the amount of TG present in the sample. As there was no large difference in the amount of amphiphilic components, i.e. DG and MG, present in the two residues studied, additional MG (Dimodan) was added to one of the residues to investigate the effect of this. The results showed that two phases, a gas phase and a yellow liquid phase, were observed in all sample mixtures studied (Table 1). To study whether intensive mixing of the two phases present would effect their phase behaviour, the sapphire cell was turned up and down a couple of times. This resulted in a hazy gas phase, while the yellow liquid phase remained transparent. However, when the cell was merely swirled around once or twice, exclusively the gas phase in immediate vicinity to the phase boarder became hazy. These results suggest that... 

Self assembly using amphiphilic components to trap drug in solution within a hydrophobic or hydrophilic core has been explored for decades for the delivery of drugs. The most notable example is that of the liposome, which, however, suffered from low entrapment efficiency, leakage, and rapid clearance by the reticuloendothelial system of the liver. This rapid clearance was reduced by the use of PEGylated phospholipids to form of the so-called sterically stabilized or stealth liposomes. ... 

Solubilization can be defined as the preparation of a thermodynamically stable isotropic solution of a substance normally insoluble or very slightly soluble in a given solvent by the introduction of an additional amphiphilic component or components. The amphiphilic components (surfactants) must be introduced at a concentration at or above their critical micelle concentrations. Simple micellar systems (and reverse micellar) as well as liquid crystalline phases and vesicles referred to above are all capable of solubilization. In liquid crystalline phases and vesicles, a ternary system is formed on incorporation of the solubilizate and thus these anisotropic systems are not strictly in accordance with the definition given above. 

Liposomes have been used by the pharmaceutical industry to deliver a range of drugs. Liposomes are made of phospholipid bilayers with one of more aqueous compartments depending on whether they are unilamellar, multilamellar, or multivesicular vehicles. Because of the bilayer structures they can adopt, they are versatile vehicles as carriers of water-soluble, oil-soluble as well as amphiphilic components. Hence, they can be used to encapsulate a wide range of food components including flavors, oils, amino acids, vitamins, minerals antimicrobials, and enzymes. Their potential applications in the food industry have been discussed by Mozafari et al. (2008)). Examples of the potential applications of liposomes in food include the delivery of cheese ripening enzymes and natural antioxidants (e.g., vitamin E). 

The surface tension of most concentrated aqueous solutions of inorganic salts, such as those employed in OD as strip solutions, is considerably greater than that of pure water. Intrusion of these solutions into microporous, hydrophobic membranes of the types used in OD is, therefore, unlikely under moderate operating pressures. However, some aqueous feeds contain amphiphilic components that may depress the liquid surface tension, and thereby reduce the critical penetration pressure. In such cases it may be necessary to use a membrane with a pore diameter of less than 0.1 p, to prevent liquid intrusion. For most applications however, membranes with a nominal pore diameter of 0.2 p have been found to be suitable. 

Our studies on solvent-impregnated resins, consisting of soluble compounds of type IB impregnated onto macroporous polymer carriers, have enabled us to conclude that a hydrophilic or amphiphilic component must be present in the polymeric network, in order to allow for fast ion diffusion inside the polymeric matrix. It is imperative that this component possesses none or minimal metal-ligand properties, so that it will not interfere with the ion selectivity of the main chelating group [6,7]. 

Microemulsions are macroscopically isotropic mixtures of at least a hydrophilic, a hydrophobic and an amphiphilic component. Their thermodynamic stability and their nanostructure are two important characteristics that distinguish them from ordinary emulsions which are thermodynamically unstable. Microemulsions were first observed by Schulman [ 1 ] and Winsor [2] in the 1950s. While the former observed an optically transparent and thermodynamically stable mixture by adding alcohol, the latter induced a transition from a stable oil-rich to a stable water-rich mixture by varying the salinity. In 1959, Schulman et al. [3] introduced the term micro-emulsions for these mixtures which were later found to be nano-structured. 

Solubilization [20, 358-360] was defined by Elworthy, Florence and Macfar-lane as the preparation of thermodynamically stable isotropic solutions of substances normally insoluble or slightly soluble in a given solvent by the introduction of an additional amphiphilic component or components [358], Like surface activity, the ability to solubilize water-insoluble compounds represents a key property in the performance of surfactants [21], Therefore, solubilization by polysoaps has raised interest from the very beginning [46-51],... 

What should be called a microemulsion is not important in itself, but since there are definition discrepancies in the publications of various authors it is important to make a point as to what will be called a microemulsion here and how to differentiate it from other self-assembly structures. The definition that is adopted here comes from the phase behavior of ternary systems that contain an amphiphile component and two immiscible so-called oil and water phases. 

Amphiphilic Components. This category includes a variety of substances that are activated by either temperature increases that create insolubility near the cloud point (low HLB nonionic ethoxylates, fatty acids, fatty amines) or in situ formation of insoluble calcium salts [22, 23],... 

One of the early hopes was that the technique could be used to create ultrathin insulating layers for field effect transistors and other electronic devices. This application is, however, bedeviled by the presence of very small defects (pinholes) in the films. These defects can be obviated by using a material whose transition temperature is well below room temperature (at which, it is assumed, fabrication takes place), such as the phospholipids found in nature as the main amphiphilic components of the ubiquitous bilayer lipid membrane that surrounds cells and their internal organelles, but these molecules are not very robust and would not have the longevity required in typical electronics applications. Another attempted application has been the creation of planar optical waveguides, but it turned out to... 

There are many additional contrast agents for MRI based on self-assembly that are being synthesized and are in the early stages of characterization. For example, Vaccaro et al. developed tumor-specific amphiphilic colloids containing Gd + complexes and the cholecystokinin-targeting CCK8 peptide. The design of the amphiphilic components... 

Later extensions of this general concept were reported by Chapman et al. [169] and Frechet [54] wherein, they reversed the amphiphilic components to produce a functionalized dendron possessing a hydrophobic head and a hydrophilic tail. The Chapman dendritic amphiphiles were derived from alky lene oxide tails and BOC terminated, Denkewalter-type dendritic heads. The Frdchet amphiphiles were obtained by attaching poly(ethylene oxide) to the focal point of a hydrophobic poly(ether) dendron as illustrated in Figure 21 [170,171]. 

The structure-forming amphiphilic component was cetostearyl alcohol. The lipophilic phase of the creams was white petrolatum. The hydrophilic phase of the coherent emulsions was constituted by distilled water conserved with methyl-p-hydroxy benzoate. 

In colloidal research, it has been often found that ILs are employed as polar and nonpolar domains moreover, they can even serve as amphiphilic components in the formation of microheterogeneous assemblies like micelles, microemulsions, etc. 

Self-assembly of amphiphilic molecules in RTILs has been recently reviewed [71-73]. The ability to form micelles, vesicles, liquid crystal, and microemulsions opens a wide range of applications. The particular advantage of using ILs in the formulation of microemulsions is their versatile use as a polar phase (substituent of water), as an organic solvent (substituent of oil), as a cosurfactant, and/or as an amphiphilic component. In many cases, the microemulsions formulated with ILs show a continuous transition from water-in-oil to oil-in-water types. 

Microemulsions are thermodynamically stable, isotropic transparent mixtnres of two immiscible liqnids (polar and nonpolar) and an amphiphilic component (nsuaUy surfactants and cosnrfactants). The microheterogeneous environments present in reverse micelles (RMs) and microemnlsions hold potential promise for apphcations in different fields owing to the nonstandard environments they produce. Often, these systems exhibit entirely different chemistry than that observed in homogeneous liquid solutions [17,18]. Microemnlsions are capable of solubilizing both polar and nonpolar substances and have wide apphcations [19, 20] in various fields such as chemical reactions [21], preparation of nanomaterials [22], and drug delivery [23]. 

Solubilisation is the process of preparation of a thermodynamically stable isotropic solution of a substance (normally insoluble or sparingly soluble in a given solvent) by incorporation of an additional amphiphilic component(s) [29]. It is the incorporation of the compound (referred to as solubilisate or substrate) within a micellar (Li phase) or reverse micellar (L2 phase) system. 

Microemulsion systems with their inner structure in the colloidal domain have been the subject of many theoretical and experimental studies due to their very broad applicability [1 ]. The name microemulsion was first introduced by Hoar and Schutman in 1943 as the name for a clear or transparent system obtained by titration of a milky white emulsion with a medium-chain length alcohol (e.g., 1-pentanol or 1-hexanol) [5]. A more general definition of the term microemulsion was given later by Danielsson and Lindman, who described it as a system, composed of water, oil and an amphiphilic component, being an optically isotropic and thermodynamically stable liquid solution [6],... 

FIGURE 9.1 Theoretical ternary phase diagram outlining the region of existence of one-phase and two-phase systems. Note the illustrative representation of the droplet w/o, droplet o/w, and bicontinuous MEs. O, oil component W, water component S, amphiphile component (surfactant/cosurfactant). 

Solubilization can enhance the uptake of the agrochemical. It is the process of preparation of thermodynamically stable isotropic solution of a substance (normally insoluble or sparingly soluble in a given solvent) by incorporation of an additional amphiphilic component(s). It is the incorporation of the compound (referred to as solubilizate or substrate) within micellar (L phase) or reverse micellar (L2 phase) system. Lipophilic (water insoluble) substances become incorporated in the L (normal micelle) phase. Hydrophilic (water soluble substances) are incorporated in the L2 phase. The site of incorporation of the solubilizate is closely related to its structure, as illustrated in Fig. 3.58 nonpolar solubilizate in the hydrocarbon core semi-polar or polar solubilizate oriented within the micelle (short or deep). 

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