Liquid crystallinity, influencing

The influence of the thermal history on the location and intensity of the a peak of PTEB can be observed in Fig. 18. It can be seen that the intensity of this relaxation measured on both E" and tanS bases decreases considerably on passing from the liquid crystalline sample... 

The phase behavior of a-ester sulfonates has been studied in detail with methyl laurate and methyl palmitate [58]. In both cases, at higher temperatures, as the surfactant concentration increases, there is a transition from an isotropic solution to a hexagonal liquid crystalline phase and finally, at high surfactant concentrations, to a lamellar liquid crystal (Fig. 4). The crystal/liquid-crys-tal phase transition occurs at even higher temperatures as the chain length increases. On the other hand, chain length has practically no influence on the... 

Membranes are composed of phospholipids and proteins. The fatty acid composition of the phospholipids in a membrane influences how it is affected by the cold. In general, as the temperature of a cell is lowered the lipids in the membrane bilayer undergo a phase transition from a liquid crystalline (fluid) state to a gel (more solid) state. The temperature at which this transition takes place is very narrow for phospholipids composed of a simple mixture of fatty acids, but is quite broad for the phospholipids in cellular membranes. It is usually implied from various methods... 

A simple example of how molecular electronic structure can influence condensed phase liquid crystalline properties exists for molecules containing strongly dipolar units. These tend to exhibit dipolar associations in condensed phases which influence many thermodynamic properties [29]. Local structural correlations are usually measured using the Kirkwood factor g defined as... 

Table II. Influence of the Main Chain Flexibility on Liquid Crystalline Phase Transitions for Polymers with Cyano-biphenyl as Nesogen...

The mixing of nematogenic compounds with chiral solutes has been shown to lead to cholesteric phases without any chemical interactions.147 Milhaud and Michels describe the interactions of multilamellar vesicles formed from dilauryl-phosphotidylcholine (DLPC) with chiral polyene antibiotics amphotericin B (amB) and nystatin (Ny).148 Even at low concentrations of antibiotic (molar ratio of DLPC to antibiotic >130) twisted ribbons are seen to form just as the CD signals start to strengthen. The results support the concept that chiral solutes can induce chiral order in these lyotropic liquid crystalline systems and are consistent with the observations for thermotropic liquid crystal systems. Clearly the lipid membrane can be chirally influenced by the addition of appropriate solutes. 

M.J. Banach, R.H. Friend, and H. Sirringhaus, Influence of the casting solvent on the thermotropic alignment of thin liquid crystalline polyfluorene copolymer films, Macromolecules, 37 6079-6085, 2004. 

This means that the partial molar area may directly be determined from the change in molecular area, when an amphiphilic molecule is introduced into a host liquid crystalline pattern. Of course, this area is the change of area per molecule at the introduction of one molecule of the substance in question and may be influenced by the interaction between the host molecules and the guest molecules. Since this interaction is an essential part of the present problem, it appears obvious that the method exactly meets the requirements. 

The crystallization process can be illustrated by a phase diagram that shows which state (liquid, crystalline, or amorphous solid [precipitate]) is stable under a variety of crystallization parameters. It provides a means of quantifying the influence of the parameters such as the concentrations of protein, precipitant(s), additive(s), pH, and temperature on the production of crystals. Hence phase diagrams form the basis for the design of crystal growth conditions (McPherson, 1999 Ducruix and Giege, 1992 Ducruix and Giege, 1999 Chayen et ah, 1996 and references therein). 

These examples indicate that the flexibility of the main chain, which is determined by its chemical constitution, directly influences the extent of the liquid crystalline state. With increasing rigidity of the main chain the motions of the mesogenic groups are more restricted. This can be noticed in an increase of the phase transformation temperature Tn. . 

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