Three-dimensional crystallinity

Electron transmission micrographs of negatively stained crystalline precipitates revealed a highly ordered three-dimensional crystalline array with intermolecular distances in good agreement with the predesigned diamond-like model. 

ITQ-21 presents excellent catalytic properties for the production of cumene, being more active and stable towards deactivation and presenting lower selectivity to NPB than a comparable beta zeolite. The benefits of ITQ-21 can be directly related to its open three-dimensional crystalline structure that favors diffusion of the products and minimizes undesired consecutive reactions. 

Fig. 6. Variation of Tm with alkyl chain length for (1) fatty acids in a monolayer state, (2) fatty acids in a three-dimensional crystalline state, and (3) normal paraffins in a three-dimensional crystalline state.

Zeolites are alumino-silicate materials containing extensive channels which connect cavities throughout giant three-dimensional crystalline structures. 

In this chapter we have considered three-dimensional ceramic constructions and nature s three-dimensional crystalline structures and glasses. There are many similarities between the construction of a ceramic work of art and the construction of a crystalline solid or glass. In both cases, units are built into a structure. The units are bonded together in a variety of ways. Both can result in pleasing works for the viewer to enjoy. A quartz crystal, made of silicon dioxide (Si02), can be just as beautiful as a carefully crafted ceramic piece. Particular elements of design make these objects beautiful. When considering ceramic pieces and natural crystals, texture is an important element. 

Ordered macroporous materials (OMMs) are a new family of porous materials that can be synthesized by using colloidal microspheies as the template. - The most unique characteristics of OMMs are their uniformly sized macropores arranged at micrometer length scale in three dimensions. Colloidal microspheres (latex polymer or silica) can self assemble into ordered arrays (synthetic opals) with a three-dimensional crystalline structure. The interstices in the colloidal crystals are infiltrated with a precursor material such as metal alkoxide. Upon removal of the template, a skeleton of the infiltrated material with a three-dimensionally ordered macroporous structure (inverse opals) is obtained. Because of the 30 periodicity of the materials, these structures have been extensively studied for photonic applications. In this paper, the synthesis and characterization of highly ordered macroporous materials with various compositions and functionalities (silica, organosilica, titana, titanosilicate, alumina) are presented. The application potential of OMMS in adsorption/separation is analyzed and discussed. 

The sequence similarities between bacteriorhodopsins and halorhodopsins from various species [17,43—45] aigue for extensive structural similarities between the two kinds of proteins. It seems likely that the tertiary structure of the halorhodopsins is a generalized bacteriorhodopsin-like arrangement, but two- or three-dimensional crystalline halorhodopsin has not been produced as yet. A crude model for halorhodopsin, based on... 

A simple substance such as water below its freezing point is a hard three-dimensional crystalline solid, and above its freezing point it is a low-viscosity Newtonian liquid. In the liquid state, the mechanical properties of such a substance are specified by its shear viscosity T], which is of course temperature- and pressure-dependent. 

Because the order due to both liquid crystallinity and three-dimensional crystallinity reduces the mobility of the amorphous regions of a polymer, as in the BDA/HD hanopolyester, the "effective Tg is higher than it would be in an amorphous, unordered polymer. Modification with EG decreased the order due to three-dimensional crystallinity, and the Tg initially decreased. 

The sheets of hydrogen-bonded cellulose chains (lying in the a-c plane of Figure 2.3d) stack on top of one another in the b-direction to form a three-dimensional crystalline structure (Figure 2.3c). In the b-direction of the unit cell the atoms that project out axially are hydrogen atoms. Fortunately, these atoms are very small so the cellulose layers can pack very close (c. 0.39 nm between layers) so close that the van der Waals forces stabilize this tight packing. Also, there is the further... 

The protein partially surrounded by detergent molecules can be used as the starting material for crystallization. Bringing a protein-detergent micelle into a three-dimensional crystalline lattice requires consideration of its hydrophobic and hydrophilic properties. In principle, there are two possible ways of arranging membrane proteins into a three-dimensional crystal, as shown by the cross-sectional views of the so-called type-I and type-II crystals in Fig. 6. 

Most of the zeolite syntheses carried out under hydrothermal conditions directly results in the formation of three-dimensional crystalline frameworks. However, several zeolites, like MCM-22 or ferrierite, can be synthesized in the form of layered precursors, which can be transformed by further thermal treatment into the three-dimensional crystal structure. These layered solids arouse an interest due to their ability to intercalate guest molecules between two neighboring zeolite layers. Using a proper treatment, layered zeolite materials can be delaminated while the structure of layers is preserved, which makes accessible all active sites located on the external surface of such catalyst. By adding proper inorganic guest molecules functioning as pillars, the control of the interlayer distance can be achieved. Such materials... 

A three-dimensional crystalline polymer often can be described as a fringed micelle (chains packed as a sheaf of grain) or as a folded chain. Regions where the polymer chains exist in an ordered array are called crystalline domains. These crystalline domains in polymers are typically smaller than crystalline portions of smaller molecules. Furthermore, imperfections in polymer crystalline domains are more frequent, and one polymer chain may reside both within a crystalline domain and within amorphous regions. These connective chains are responsible for the toughness of a polymer. Sharp boundaries between the ordered (crystalline) and disordered (amorphous) portions are the exception but do occur in some instances such as with certain proteins, poly(vinyl alcohol), and certain cellulosic materials. Highly crystalline polymers exhibit... 

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