Molecules form-anisotropic

Notable in the tricolorin A (106) solid state is the presence of 18 water molecules in the unit cell, and an anisotropic repartitioning of the hydrophobic and hydrophilic sections. The water molecules form a dense network that creates a dividing layer between the hydrophilic faces (see Fig. 6). The high water content indicates that the conformation in the solid state is not dominated by intermolecular forces and could be indicative of a similar conformation in both solution and supermolecular... 

If the crystals of 1 are exposed to bromine vapor, addition to the C=C double bond occurs without difficulty, as the molecules can anisotropically migrate along the cleavage plane and the quantitatively obtained trans adduct does not include large amounts of bromine. The gas-solid addition of 2 is more complicated. The initially formed crystalline adduct keeps large quantities of additional bromine and eliminates HBr upon standing and in solution by forming lactones. Thus, mixtures of products arise because consecutive reactions... 

Randomly distributed dipolar molecules form an isotropic medium characterized by a single refractive index n. When these molecules are more or less aligned in an electric field the medium becomes anisotropic and its optical properties must be described by two refractive indices. The Kerr cell consists of a glass vessel fitted with two parallel optical windows and two metal electrodes (Figure 2.11). The cell contains a liquid or a gas (solids can also be used) when an electric field exists between the electrodes the phase difference between the electric vectors is proportional to the square of the field and to the value of the electrical Kerr constant of the dielectric... 

The crystal structure and electrical conduction properties of (Et4N)0,5[Ni(dmit)23 (where dmit = isotriethione dithioiate) have been reported.120 In the crystal, face-to-face stacking and side-by-side arrangement of Ni(dmit)2 molecules form a two-dimensional S—S network. The compound is an anisotropic semiconductor with a maximum conductivity of 4.5 x 10-2 Q"1 cm 1 in the stack direction.120... 

Although the great majority of petroleum and coal-based pitch materials, as well as model compounds such as polyvinyl chloride, acenaphthylene, decacyclene and polynuclear aromatic hydrocarbons, form anisotropic graphitizable carbons, it is an almost impossible task to predict the type of optical texture of a coke from an elemental analysis of the pitch. The size, shape and reactivity of peri-condensed polynuclear aromatic molecules in the products of pyrolysis of a pitch play a more important role in determining optical texture. 

For molecules with anisotropic polarizabilities, where the assumption Piseries solution in the form times powra s of a r gM The contribution to Be of the lead term in the series proportional to vanishes on averaging over all orientations if the intomolecular potential is a function of fu only. For isotropically polarizable molecules the lead term also vanishes, leaving the series equivalent to the second term on the right side of equation 3a). The lead term in this series, (4Treo) 2<4 i2, is exactly what is obtained by setting the denominator of the second term in equation (23a) equal to one. 

Many computers, such as laptops, have flat-panel screens or displays that contain liquid crystals (Bahadur 1990). Liquid crystals are composed of small semirigid molecules that are elliptical or oblong in shape and spontaneously orient, forming anisotropic fluids (Collings 1990). Liquid crystals commonly used in flat-panel displays have orientational order but do not have long-range positional order. The direction of the preferred orientation in a liquid... 

CB is 4-cyano-4 -pentylbiphenyl. Liquid-crystal phases can also form when amphiphilic molecules associate to form anisotropic structures which, in turn, spontaneously order into liquid-crystalline phases. 

One of the few exceptions are molecules like p-azoxyanisol, p-azoxyphenetol and anisaldazine, which form anisotropic liquids and for which Wolf [Physik and Chemie der Grenzjlachen. Vol. 1, Springer (1957), p. 44) reports y T) curves with kinks. 

In contrast to polypeptides that have many possible conformations, poly(hexyl isocynate) is known to have a stiff rodlike helical conformation in the solid state and in a wide range of solvents, which is responsible for the formation of a nematic liquid crystalline phase.45-47 The inherent chain stiffness of this polymer is primarily determined by chemical structure rather than by intramolecular hydrogen bonding. This results in a greater stability in the stiff rodlike characteristics in the solution as compared to polypeptides. The lyotropic liquid crystalline behavior in a number of different solvents was extensively studied by Aharoni et al.48-50 In contrast to homopolymers, interesting new supramolecular structures can be expected if a flexible block is connected to the rigid polyisocyanate block (rod—coil copolymers) because the molecule imparts both microphase separation characteristics of the blocks and a tendency of rod segments to form anisotropic order. 

A number of different types of molecules form liquid-crystalline phases. What most of them have in common is that their physical properties are anisotropic. Either the molecular shape is such that the length of... 

A comparison among the polymerizations in the different states is summarized in Table 1. The monomer molecules form low-dimensional and anisotropic assemblies in the inclusion and solid states although they form three-dimensional and isotropic assemblies in the solution... 

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