Three-dimensional lamellar crystals

Smectics Be, E, G, H, in fact, are three-dimensional lamellar crystals with positional correlations of molecules both inside and between the smectic layers. They differ from each other by the type of the crystalline lattice. The crystalline Be phase forms a true hexagonal lattice with molecules orthogonal to layers. It does not support the shear parallel to layers [10]. 

When the nuclei are arranged regularly in space without leaving a vacancy, the crystal can be represented by a giant molecule (macromolecular crystal) and, as in molecules, the molecular orbitals would be more or less localized, which step by step assure the bonds. Two typical cases are possible here. The network of the bonding orbitals could extend itself either in three special directions or in only two or one direction. In the first case, one would speak of a three-dimensional macromolecular crystal, as a true generalization of a molecule of finite size, while in the other case, one would have either a two-dimensional lamellar network or a monodimensional... 

SmA is a one-dimensional lamellar crystal with the interlayer distance almost rigidly fixed. In order to discuss elasticity we need an additional variable that would describe the lamellar structure. Consider a small distortion of smectic layers [17]. In Fig. 8.23 dash and solid lines indicate undisturbed and distorted layers, respectively. Short rods perpendicular to the lowest solid line indicate local directors, which are always perpendicular to the layers. Now, we introduce a layer displacement along the z-axis, u = Uz.ln fact, it is a scalar field y, z), depending generally on aU the three co-ordinates. Its derivatives describe two types of elasticity ... 

Lyotropic lamellar (La) liquid crystals (LC), in a form of vesicle or planar membrane, are important for membrane research to elucidate both functional and structural aspects of membrane proteins. Membrane proteins so far investigated are receptors, substrate carriers, energy-transducting proteins, channels, and ion-motivated ATPases [1-11], The L liquid crystals have also been proved useful in the two-dimensional crystallization of membrane proteins[12, 13], in the fabrication of protein micro-arrays[14], and biomolecular devices[15]. Usefulness of an inverted cubic LC in the three-dimensional crystallization of membrane proteins has also been recognized[16]. 

On the other hand, studies with three-dimensional isotropic lamellar matrices have shown that Azone is a weakly polar molecule, which can occupy the interfacial region as well as the hydrocarbon interior of bilayers [86,87]. The contrasting observations of Azone promoting the assembly of reversed-type liquid-crystal phases (e.g., reversed hexagonal and reversed micellar) in simple model lipid systems [88-90], while also favoring the formation of lamellar structures in one of these mixtures [91], adds further confusion to the discussion [92]. This notwithstanding, the studies by Schiickler and co-workers [91] emphasize the differences in the calorimetric profiles of intact human stratum comeum (HSC) and model SC lipid mixtures Although these systems are clearly useful and versatile, extrapolation of inferences from model lipids to the intact membrane must be performed with caution. 

Titanium Silicalite-2 (TS-2), structurally similar to TS-1, could be prepared likewise using tetrabutylammonium hydroxide as the template [13, 14]. Titanium aluminum Beta (Ti,Al-[3) was prepared by hydrothermal synthesis from amorphous silica, sodium aluminate, tetraethyltitanate and tetraethylammonium hydroxide [15]. The presence of A1 was necessary for the crystallization of the product. Al-free Titanium Beta (Ti-[3) could be obtained in the presence of particular templates, such as dibenzyldimethylammonium hydroxide [16]. Titanium Mordenite (Ti-MOR), conversely, was obtained by post-synthesis insertion of Ti to dealuminated Mordenite [17]. Ti-MWW (Ti-MCM-22) was obtained by the synthesis of the lamellar precursor of Ti,B-MCM-22 followed by acid treatment to remove most of the boron and extra-framework Ti and finally calcination to burn out the template and bring about the condensation of lamellae into the three-dimensional MWW structure [18]. Ti is present in a number of different environ-... 

One or more crystalline lamellar (Lc) phases may be formed by all phospholipids at low temperature and/or low levels of hydration. When long and short range order is found in three dimensions then the result is a 3D lamellar crystal, which is a true crystal. The three dimensional crystalline order results from the close packing of two dimensional phospholipid crystalline sheets (Figure 1.90). In all crystalline and ordered states, phospholipid close packing and molecular conhguration is dehned in terms of a number of parameters. These parameters are ct—the mean cross sectional area of a fatty acid alkyl chain perpendicular to the chain axis, 4>—the tilt angle of the chain with respect to bilayer plane, —the thickness of the... 

P-ll - A study on the crystallization of a lamellar aluminophosphate APO-M to a three-dimensional aluminophosphate APO-CJ3... 

In crude oil and water systems asphaltenes are adsorbed at the water-oil interface and flocculate yielding a three-dimensional structured film (as Mesophase C) (43). Such structured films at the W/0 interface were verified by Sif-fert et al. (44). They separated oil, water, and a sticky mass between sheets in asphaltene particles for fliis black mass. These regularly stacked lamellar structures have close similarity to surfactant liquid crystals. 

Crystallization results basically in the succession of two events the primary nucleation of a new phase and then the three-dimensional growth of lamellae these steps can be followed by lamellar thickening, fold surface smoothing, or reorganization into more perfect crystals. As reported by others, with increasing the annealing temperature in PVDF/PMMA blend film, the amount of a phase increases due to easier local internal chain rotation at higher temperature and most of p and y form convert to a form. 

He found that n has a linear dependence on the cooling rate a. When n changes from 2 to 3 with the increase of cooling rate, crystallization may change from two-dimensional lamellar growth to three-dimensional spherulitic growth, while Kc keeps constant. Compared to the following methods. The Jeziomy method lacks of a necessary theoretical basis. 

SmBcr Da, X T(0) Crystalline lamellar phase with upright molecules and hexagonal lattice. True three-dimensional positional order. Soft crystal with small shear elastic modulus... 

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