Liquid crystalline systems

Liquid Crystalline Systems. Conventional photoconductive polymers are amphorous or systems withlow order. In the case of PVK, the hole moves by hoppiag between the pendent carba2ole groups. The hole mobilities are usuaUylow, cm /Vs, due to a trap-dominated hoppiag... 

The use of ordered supramolecular assemblies, such as micelles, monolayers, vesicles, inverted micelles, and lyotropic liquid crystalline systems, allows for the controlled nucleation of inorganic materials on molecular templates with well-defined structure and surface chemistry. Poly(propyleneimine) dendrimers modified with long aliphatic chains are a new class of amphiphiles which display a variety of aggregation states due to their conformational flexibility [38]. In the presence of octadecylamine, poly(propyleneimine) dendrimers modified with long alkyl chains self-assemble to form remarkably rigid and well-defined aggregates. When the aggregate dispersion was injected into a supersaturated... 

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. 

Sehuetze, W., and Mueller-Goymann, C.C., Mutual interactions between nonionie surfaetants and gelatin—investigations in eubie liquid crystalline systems and mieellar systems. Colloid Polym. Sci., 269 85-90 (1992). 

The results of colloid science play a crucial role in our everyday lives From hair spray to shower gel, from the lacquer we are using to repaint our front doors to the LCD displays on our new computers, colloidal and liquid crystalline systems are omnipresent in our immediate surroundings. 

Further calculations on aromatic polyesters, polyamides and liquid crystalline systems ... 

In Section 3.4.6 it was noted that chiral mesophases behave as chiral perturbation moieties for achiral molecules inserted to the mesophases. Here, only relations between the observed signs in LCICD and the pitch-dependent CD in liquid crystalline systems, and the helical sense of the liquid crystalline phases are described. 

Tihe term lyotropic mesomorphism is used to describe the formation of thermodynamically stable liquid crystalline systems through the penetration of a solvent between the molecules of a crystal lattice. In contrast to the thermotropic mesomorphism shown by many pure substances, lyotropic mesomorphism always requires the participation of a solvent. Lyotropically mesomorphous systems, however, are usually as sensitive to changes in temperature as thermotropic systems. So far, lyotropic mesomorphism has been observed almost exclusively in lipid systems containing water. Lipids that show lyotropic mesomorphism frequently... 

Here % specify the transformation from coordinate system j to system i. In Equation 3 only Dq q (Qdm) varies with the molecular motion. Since amphiphilic liquid crystalline systems generally are cylindrically symmetrical around the director Dq q (nDM) = 0 if qf 0. If it also is assumed that a nucleus stays within a domain of a given orientation of the director over a time that is long compared with the inverse of the quadrupole interaction, one now obtains for the static quadrupole hamiltonian... 

Ref. 13 contains a more complete discussion of static quadrupolar effects for amphiphilic mesophases. That work also includes a treatment of counterion quadrupole relaxation for liquid crystalline systems a brief outline of this discussion is given in the next section. 

The experimental observations could be consistently explained if the general tilt structure (SmCo) inside the layers is assumed. For most bent-core smectics the polar vector is perpendicular to the tilt plane, defined by the layer normal and averaged long axis direction, just as polarization in the ferroelectric rod-like liquid crystalline systems. However, since in the bent-core liquid crystals the polar order is decoupled from the tilt order, the polar director can in general have any direction in space thus it can also have a non-zero component along the layer normal. This can be achieved by a combination of tilting (rotation around the polar director) and leaning (rotation around the direction perpendicular to the polar director) of... 

Cyclic trimeric and tetrameric phosphazenes with mesogenic side groups also generate liquid-crystalline systems.245,249... 

Subject areas for the Series include solutions of electrolytes, liquid mixtures, chemical equilibria in solution, acid-base equilibria, vapour-liquid equilibria, liquid-liquid equilibria, solid-liquid equilibria, equilibria in analytical chemistry, dissolution of gases in liquids, dissolution and precipitation, solubility in cryogenic solvents, molten salt systems, solubility measurement techniques, solid solutions, reactions within the solid phase, ion transport reactions away from the interface (i.e. in homogeneous, bulk systems), liquid crystalline systems, solutions of macrocyclic compounds (including macrocyclic electrolytes), polymer systems, molecular dynamic simulations, structural chemistry of liquids and solutions, predictive techniques for properties of solutions, complex and multi-component solutions applications, of solution chemistry to materials and metallurgy (oxide solutions, alloys, mattes etc.), medical aspects of solubility, and environmental issues involving solution phenomena and homogeneous component phenomena. 

Many relatively simple amino- and hydroxyanthraquinone derivatives show a high degree of order in liquid-crystalline systems and are therefore suitable as dichroic dyes for guest-host displays. Several new dyes for this application have been described. For example, 9 is a blue dichroic dye [4],... 

The liquid crystalline state is frequently recognized most simply by heating a thermotropic solid. If the solid transitions to a turbid system before becoming an isotropic liquid, the turbid system is most likely a liquid crystalline system. On cooling, the liquid may revert to the turbid system on the way to the solid phase. However, if heated above a molecular transition point, the material may not return to the turbid state on the way to becoming a solid. 

Abstract The preparation of chiral functional materials with new, improved, and interesting properties is aided tremendously by control of the spatial arrangement of the functional units within them. The use of non-covalent interactions is absolutely critical in this regard, and the molecular-supramolecular balance has to be strictly controlled. The conducting, magnetic and optical properties of chiral materials whose function is profoundly influenced by supramolecular chemistry will be reviewed. Special emphasis is placed on the control of helical arrangements in liquid crystalline systems, in which both chiral induction and spontaneous resolution are important phenomena which can be controlled. 

Supramolecular structures obtained via self-assembly processes may be named as another future topic, which just starts an increasingly rapid development.294 By some examples it was already demonstrated how molecular chirality may by translated into supramolecular chirality in such self-assembled structures and this may lead not only to new, improved host-guest systems but also eventually to new materials in a more general sense. Liquid-crystalline systems or materials for nonlinear optics may be mentioned just as two examples. 

In this review, we discuss cases of formation of polymeric liquid crystalline systems associated with the solutions of so-called rigid-chain polymers. 

In principle, lyotropic liquid crystalline systems are such systems in which liquid crystalline ordering appears only in the presence of a solvent, the solvent being selective and the dissolved substance having amphiphylic properties. Soaps, lipids, and some dyes in an aqueous medium may serve as examples of such systems. 

An earlier study of the molecularly doped polymer liquid crystalline system shown in Figure 6.9 revealed more complex behavior (27, 32). In this study, the amount of induced nonlinearity was path dependent, with the largest observed value occurring when poling was done near Tg ( 25 C). The host polymer exhibits a nematic-to-isotropic transition at = 100 C and a nematic texture between Tg and. Poling at 50 C produces a decrease in approximately 1 order of magnitude. The l/T dependence... 

Emulsions, microemulsions, and liquid crystalline systems are suspensions of deformable particles, and many of the principles stated earlier for suspensions are valid to a similar extent. The effect of the phase volume, however, is less pronounced. ... 

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