Microstructures bilayer structure

In summary, we see that a surprisingly limited number of amphiphiles is required to form a stable bilayer. And although more amphiphiles are readily accepted into the microstructure, an upper limit is eventually reached. The evolution of bilayer structure from one limit to the other can be further appreciated by examining the density profiles of tail particles and free water particles within the bilayer these are shown in Figs. 5 and 6, respectively. As is... 

In addition to bilayered electrodes with a functional layer and a support layer, electrodes have also been produced with multilayered or graded structures in which the composition, microstructure, or both are varied either continuously or in a series of steps across the electrode thickness to improve the cell performance compared to that of a single- or bilayered electrode. For example, triple-layer electrodes commonly utilize a functional layer with high surface area and small particle size, a second functional layer (e.g., reference [26]) or diffusion layer with high porosity and coarse structure, and a current collector layer with coarse porosity and only the electronically conductive phase (e.g., reference [27]) to improve the contact with the interconnect. 

It is seen from the discussion above that Cu is electrodeposited in vias and trenches on a bilayer a barrier metaVCu seed layer. When the barrier layer is composed of two layers (e.g., TiN/Ti), Cu is electrodeposited as a trilayer a barrier bilayer/Cu seed layer. This type of underlayer for electrodeposition of Cu raises a series of interesting theoretical and practical questions of considerable significance regarding the reliability of interconnects on chips. In Section 19.1 we have noted that interconnect reliability depends on the microstructural attributes of electrodeposited Cu (for Cu-based interconnects). These microstractural attributes, such as grain size, grain size distribution, and texture, determine the mechanical and physical properties of the thin films. Thus, one basic question in the foregoing series of questions is the problem of the influence of the underlayer barrier metal on the microstructure of the Cu seed layer. The second question is the influence of the microstructure of the Cu seed layer on the structure... 

Micellar solutions are isotropic microstructured fluids which form under certain conditions. At other conditions, liquid crystals periodic in at least one dimension can form. The lamellar liquid crystal phase consists of periodically stacked bilayers (a pair of opposed monolayers). The sheetlike surfactant structures can curl into long rods (closing on either the head or tail side) with parallel axes arrayed in a periodic hexagonal or rectangular spacing to form a hexagonal or a rectangular liquid crystal. Spherical micelles or inverted micelles whose centers are periodically distributed on a lattice of cubic symmetry form a cubic liquid crystal. 

Giulieri, F., and Krafft, M. R (2003), Tubular microstructures made from nonchiral single-chain fluorinated amphiphiles Impact of the structure of the hydrophobic chain on the rolling-up of bilayer membrane, J. Coll. Interf. Sci., 258, 335-344. 

Oils. SANS has been used to establish the effect of the addition of a hydrophobic guest (dodecane) on the behavior of liquid crystalline phases, in particular the lamellar and columnar phases of mixtures of the non-ionic surfactant C16E7 with D2O, as well as to determine the distribution of the hydrophobic guest in the microstructure. SANS showed that the presence of the hydrophobic guest molecule, in some cases, stabilized a particular phase structure, (for example lamellar phases formed at lower temperatures in the presence of dodecane) while in other cases it destabilized it, eventually (depending upon the concentration of dodecane added) causing the phase to disappear. In the lamellar phase, dodecane was found to be totally segregated in the center of the bilayer. 

Vesicles form when a surfactant bilayer encapsulates an aqueous core (Fig. 1). The microstructure resembles that of a biological cell in which the plasma membrane has been replaced by a surfactant bilayer. These structures can form either spontaneously or as a result of shear or other processing of lamellar liquid crys-... 

It was suggested [284] that the perforated lamellar phase may form via the growth of branched and multiconnected threadlike micelles. Interconnection of threadlike micelles reduces the overall curvature of the monolayer making up the micelles and thereby reflects a preference for microstructures of decreasing curvature [119]. The suggested morphological sequence for the system cetylpyridinium chloride-hexanol-brine is spheres, small disks, long capped cylinders, branched cylinders, perforated bilayers, smooth bilayers, loose network of connected bilayers (foamlike structure), and multiphasic domain [284]. 

The interfadal activity of amphiphiles is but one manifestation of their discordant intramolecular makeup. These molecules can also self-assemble in solution to form a variety of microstructures, such as micelles and vesicles to name a few. Of course structures based on a bilayer motif, such as vesicles, have direct biological relevance as they serve as models for cell membranes. 

Segura el al. combines Tarazona s WDA DFT for hard-spheres with Wertheim s thermodynamic perturbation theory and has been used in a number of studies of associating fluids in pores and with functionalized walls in the limit of complete association a DFT for polymeric fluids is obtained in this method. Based on these works, Chapman and co-workers have presented the interfacial-SAFT (iSAFT) equation, which is a DFT for polyatomic fluids formulated by considering the polyatomic system as a mixture of associating atomic fluids in the limit of complete association this approach allows the study of the microstructure of chain fluids. Interfacial phenomena in complex mixtures with structured phases, including lipids near surfaces, model lipid bilayers, copolymer thin films and di-block copolymers, have all been studied with the iSAFT approach. 

A section through the phase prism at constant surfactant concentration ( Shinoda-cut ) is particularly illustrative. This shows the interrelation between the temperature-dependence and the dependence on the water-to-oil ratio. By choosing the surfactant concentration to be slightly above 0, one obtains a phase behaviour that is illustrated schematically in Figure 17.4. This section contains a rich variety of microstructures, e.g. the microemulsion phase which has a surfactant monolayer structure and the lamellar phase and the sponge phase which both have a bilayer... 

Before we come to the microstructures there are several facts that are worth emphasizing. Note that the phase boundaries between the different phases are given by more or less straight lines, which means that the mixing ratio for the micelles is constant at the phase boimdaries and does not depend on the concentration. Notice also that the equimolar mixtures of surfactant and cosurfactant are in the middle of the wide region. The combination therefore acts like a real double-chain surfactant. The phases from Li to are actually subphases of L , as has been demonstrated by freeze fracture electron micrographs. They consist of bilayer-type structures [13] but the topology of the bilayers is quite different. 

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