Cooperative ordering

Thermotropic phases are those that occur in a certain temperature range. If the temperature is raised too high, thermal motion will destroy the delicate cooperative ordering of the LC phase, pushing the material into a conventional isotropic liquid phase. At too low a temperature, most LC materials will form a conventional (though anisotropic) crystal. Many thermotropic LCs exhibit a variety of phases as the temperature is changed. For instance, a particular mesogen may exhibit various smectic and nematic (and finally isotropic) phases as temperature is increased. 

Heat capacity data below 300 K are based on the measurements of Kostryokova (8) (2-30 K) and Busey and Giauque (9) (14.14-336.36 K). The two sets of data are joined smoothly via a least squares procedure Kostryokova s values (8) are higher than those of Busey and Glaugue (9) by 5.3% at 15 K and 0.3% at 30 K. The results of Busey and Giauque (9) indicate a sharp lambda peak at 52.35 K which is apparently associated with the cooperative ordering of the magnetic moments of the nickel ions. C near the... 

The corrections mentioned, however, are rather approximate and thus one can enlarge the set of magnetic parameters for a temperature-independent term amol which compensates these uncertainties. Also, some cooperative ordering applicable at a low temperature can be included through the molecular field correction Z so that the theoretical function to be considered becomes... 

To what extent is the cooperative ordering process leading to the formation of M41S materials influenced by the addition of RSi(OR )3 What degree of functionalization can be attained in the final mesoporous material after removal of the templating SDAs ... 

Approximate solution of the cooperative order-disorder problem We define the degree of positional order as q = 22 —, where J is the fraction of molecules in the -sites, and the degree of orientational order as s = 25 —1, where is the fraction of molecules in 1-orientations. If N is the total number of molecules in the system, there are evidentiy... 

As these cosolvents contain both hydrophilic and hydrophobic groups, the same molecule can induce opposite effects in water. The hydrophilic part can interact with water to form strong HBs, while the hydrophobic part may induce cooperative ordering in the system by a hydrophobic hydration effect. These two effects combine together to regulate the extensive HB network of water in their aqueous binary mixtures that is reflected in strong, often anomalous non-ideal behavior in many physical properties such as viscosity, density, dielectric constant, excess mixing volume, surface tension, heat of formation, etc. 

Order-disorder conformational transitions very often occur on changing physical and/or chemical conditions of polysaccharide solutions. DMSO, for example, is the solvent, which is commonly used as co-solvent for stabilizing or destabilizing ordered solution conformations. Schizophyllan, a triple helical polysaccharide with a [P-D-(l-3)-glc] backbone exhibits a highly cooperative order-disorder transition in aqueous solution. When small quantities of DMSO are added to aqueous solutions the ordered state is remarkably stabilized, as has been observed in the heat capacity curves by means of the DSC technique. ... 

In macromolccules with strong intramolecular interactions, a cooperative order-disorder (helix-coil) transition is possible, which is of prime importance for solutions containing proteins and nucleic acids. The formation of a system of intrsunolecular H-bonds among the groups of the main chain, stabilized by hydrophobic interactions, leads to the helix conformation. As temperature rises, or an active solvent is introduced, intramolecular H-bonds break down, and the helix-coil transition occurs. It is reversible with decreasing temperature or removing the active. solvent, respectively. ... 

Here H corresponds to the magnetic field at the R site, which may originate from cooperative ordering, i.e. an internal field, or from an applied, external field. A represents the mean-field parameter. The mean-field approximation leads to a reasonable description of the influence of magnetic ordering on the CEF splitting when the exchange... 

Orientation of water molecules around a charged hydrophilic surface. The molecules closest to each surface exhibit a diffuse layered structure (oscillatory hydration force regime) beyond that there may be some cooperative ordering (monotonic hydration force regime). Because the mean orientations of the water molecules are antiparallel on either side of the midplane, the net hydration force is repulsive. Bottom cooperative alignment of water molecules between two hydrophobic surfaces, resulting in a net attractive solvation force. From Israelachvili [12],... 

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