Anisotropic ordering

The idea of electronic conductivity in the crystals of this cluster is stimulated by the metallic reflectance of the crystals. A potential conductivity is expected to be anisotropic because of the anisotropic order of the clusters inside the crystal. As a consequence, the electric resistance is expected to be smaller in the direction of the tubes than in the vertical direction where there is no graphite-like bridging between the clusters. 

On a molecular level the director is not rigorously defined, but the molecular director is typically considered to be the average long axis of the molecules, oriented along the macroscopic director with some order parameter less than one. This type of anisotropic order is often called long-range orientational order and, combined with the nonresonant optical properties of the molecules, provides the combination of crystal-like optical properties with liquidlike flow behavior characteristic of liquid crystals. 

There is now an impressive repertoire of anisotropic ordering media which can be employed for the purpose of establishing a weak degree of... 

While for m-l.c. s the state of order is only determined by the anisotropic interactions of neighbouring molecules, for the polymers additionally a disturbing effect of the backbone via the flexible spacer on the anisotropic order of the mesogenic side chains is to be expected and vice versa. Therefore it is of interest to investigate whether... 

While for nematic polymers the statistical distribution of the centers of gravity of the mesogenic side chains is compatible with a more or less statistical main chain conformation, for smectic polymers a three dimensional coil conformation is no longer consistent with the layered structure of the mesogenic side chains. The backbone has to be restricted in its conformation, which will cause a more pronounced interaction between the main chain and the anisotropically ordered mesogenic side chains, compared to nematic and cholesteric polymers. 

For example, with filler coke blends, maximum incompatibility has been found for blends of flaky, low-modulus, oxidation-resistant, anisotropic (ordered) delayed coke, and round, high-modulus, oxidation-sensitive, relatively-isotropic (disordered) fluid coke. 

The hydrogen-bond mediated self-assembly of nanoparticles and polymers provides a versatile and effective method to control interparticle distances, assembly shapes, sizes, and anisotropic ordering of the resultant nanocomposites. This approach presents the bottom-up strategy to fabricate nanomaterials from molecular building blocks, which have great potential for assembling and integrating nanoscale materials and particles into advanced structures, systems, and devices. 

Fig. 2.12. Proton nuclear relaxation rate 1/Ti vs temperature of (TMTSF)2C104. The solid line is a calculation with an anisotropic order parameter. Prom [117]...

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. 

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