Liquid crystals molecular

The response of liquid crystal molecular orientation to an electric field is another major characteristic utilised for many years in industrial applications [44] and more recently in studies of electrically-induced phase transitions [45]. The ability of the director to align along an external field again results from the electronic structure of the individual molecules. 

Keywords Smectic liquid crystals, Molecular conformations, polar and steric frustrations, Polyphilic and perfluorinated mesogens. X-ray diffraction... 

Hird, M. and Toyne, K.J. (1998) Fluoro Substitution in Thermotropic Liquid Crystals. Molecular Crystals and Liquid Crystals, 323, 1-67. 

Obviously, chirality is an essential property in molecular chemistry, and knots are exciting systems in this context. With a touch of fantasy, it could be conceived that some of the chemical processes for which chirality is essential (enan-tioselection of substrates, asymmetric induction and catalysis, cholesteric phases, and ferroelectric liquid crystals molecular materials for non linear optics...) could one day use enantiomerically pure knots. 

Supermolecular level liquid crystals are not of major concern in this review. In fact, they form a class of materials which should best be separated from the normal liquid crystals . Although there are structural similarities to the molecular liquid crystals, molecular motion and transition behavior of these liquid crystals based on supermolecular structure is completely different. 

Phenylacetylene derivatives, (V), were prepared by Tang [2] and converted into the corresponding polyacetylenes, (VI), as illustrated below, containing a side-chain liquid crystal molecular architecture of backbone + spacer + mesogenic group. These products were subsequently used in electronic and mechanical applications. 

In normal liquids, most molecules move isotropically and dipolar couplings are averaged to 0. In static solids and in liquid crystals, molecular motion is non-existent or anisotropic and dipolar couplings are observed. In solids, dipolar couplings are obscured by chemical shift anisotropy but in liquid crystals, they are observed and can be large, up to the kHz range [423], The size of the direct dipolar coupling (Dy) between nuclei i and j is ... 

Kato T (2000) Hydrogen-Bonded Liquid Crystals - Molecular Self-Assembly for Dynamically Functional Materials. 96 95-146 Katz E, see Shipway AN (2001) 99 237-281 Kauffmann GB, see Jorgensen CK (1990) 73 227-254 Keijzers CP, see Willemse J (1976) 28 83-126 Kelly JM, see Moucheron C (1998) 92 163-216... 

Hydrogen-Bonded Liquid Crystals Molecular Self-Assembly for Dynamically Functional Materials... 

New Engineering Thermoplastics New High Performance Thermosets Thermotropic Liquid Crystals Lyotropic Liquid Crystals Molecular Composites Advanced Composites Non-Linear Optical Polymers Electronically Conducting Polymers... 

L. Beresnev and L.M. Blinov, Ferroelectric liquid crystals molecular aspects, Mendeleev J. All-Union Chem. Soc. 28, 149-155, (1982). 

I phase transition point in 5CB liquid crystal. Molecular Crstals and Liquid Crstals, 366, pp. 183. 

Soft matter science is nowadays an acronym for an increasingly important class of materials, which encompasses polymers, liquid crystals, molecular assembhes building hierarchical structmes, and the whole area of colloidal sciences. Common to all of them is that fluctuations and thus the thermal energy T and the entropy play an important role. Soft then means that these materials are in a state of matter that are neither simple liquids nor hard solids of the type studied in hard condensed matter, hence sometimes soft matter firms also under the name complex fluids. 

The selected examples in this chapter demonstrate the success of the development of photoswitchable molecular materials through the rational designs based on the coupling of photochromic moieties into molecules with different functions, such as luminescence, nonlinear optics, liquid crystal, molecular machine, receptor, electrical con-ductor/semiconductor, and many others. It is important to emphasize that photoswitchable materials are not confined only to the selected areas in these examples. With the understanding of both the photoswitching processes and the functional properties at the molecular levels, materials that possess different varieties of photoswitchable functional properties can be readily designed and synthesized. 

Fig. 3.7.3 Liquid crystal molecular orientation on obliquely evaporated SiO surfaces (a) without treatment by surface active agent, (b) with treatment by surface active agent.

In LCD devices, liquid crystal materials are usually sandwiched between two glass substrates carrying alignment film with a gap of 1-10 pm. the influence of the alignment film on the substrates, liquid crystal molecular orientations are determined. Typical orientations are shown in Fig. 4.1.1. 

Liquid crystal molecular orientation model at various voltages, (a) No voltage, (b) Low voltage, (c) High voltage. R = rubbing direction. Source Nose, T., S. Masuda, and S. Sato. 1992. Japanese Journal of Applied Physics Part 1,31(5), 1643-1646. With permission.)... 

The existence or nonexistence of mirror symmetry plays an important role in nature. The lack of mirror symmetry, called chirality, can be found in systems of all length scales, from elementary particles to macroscopic systems. Due to the collective behavior of the molecules in liquid crystals, molecular chirality has a particularly remarkable influence on the macroscopic physical properties of these systems. Probably, even the flrst observations of thermotropic liquid crystals by Planer (1861) and Reinitzer (1888) were due to the conspicuous selective reflection of the helical structure that occurs in chiral liquid crystals. Many physical properties of liquid crystals depend on chirality, e.g., certain linear and nonlinear optical properties, the occurrence of ferro-, ferri-, antiferro- and piezo-electric behavior, the electroclinic effect, and even the appearance of new phases. In addition, the majority of optical applications of liquid crystals is due to chiral structures, namely the ther-mochromic effect of cholesteric liquid crystals, the rotation of the plane of polarization in twisted nematic liquid crystal displays, and the ferroelectric and antiferroelectric switching of smectic liquid crystals. 

A glass substrate, which has a transparent common electrode on its inner surface, is placed facing this matrix pixel substrate as shown in Fig. 7 (b). A liquid crystal molecular alignment layer is provided on the... 

Finally, two examples have been presented which show the relationship between packaging techniques and liquid-crystal molecular orientation. 

The NMR spectra of molecules in a liquid crystalline environment, either mesogenic molecules or solutes, are dominated by second-rank tensorial properties (T) such as the shielding tensor (o, the dipolar and indirect spin-spin interactions (D,j and Jjj) and, for nuclei with 7>l/2, the quadrupolar interaction (qj). In most liquid crystals, molecular reorientations and internal motions reduce these interactions to a well-defined average, without the loss of all information. Moreover, molecular translational diffusion averages out to zero the intermolecular interactions, which thus do not complicate the partially averaged spectra. In the usual high-fleld approximation, in NMR experiments we measure T, the component of... 

In order to use liquid crystalline polymers as commercial optical films, it is necessary to achieve both the immobilization of the liquid crystal molecular oriented structure and the orientation control of the liquid crystalline polymer. However, in the 1980s there was no technology that could satisfy both requirements and it was necessary to develop it ourselves. The key phrase at that time was do not be bound by common sense. ... 

Immobilization of the Liquid Crystal Molecular Oriented Structure... 

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