Liquid crystalline propertie

I)(. p end ing upon the parameters chosen, simulations performed using the Gay-Berne potential show behaviour typical of liquid crystaUine materials. Moreover, by modifying the potential, 111. can determine what contributions affect the liquid crystalline properties and so help to suggest what types of molecule should be made in order to attain certain properties. 

Both 4,5- and 3,6-disubstituted phthalonitriles are commonly used to prepare phthalocyanines with liquid crystalline properties. An example of the Rosenmund-von Braun reaction is shown below.107... 

Wholly aromatic polyesters, in which both R1 and R2 are aromatic, are either high-7 amorphous polymers or veiy high melting semicrystalline polymers that often exhibit liquid crystalline properties. 

Thermotropic liquid-crystalline properties of different metal alkanesulfonates are studied by microscopy and X-ray diffraction [59]. Sodium soaps show smectic polymorphism of smectic A and smectic B phases. Ammonium soaps only show smectic A phases but polymorphism in the crystalline state. Calcium soaps show columnar mesophases. In Figs. 32 and 33 some textures and x-ray diffraction patterns are depicted. 

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... 

The first report on the liquid crystalline properties of these compounds was published by Gray and Mosley [44] in 1976. The series of 4 -n-alkyl-4-cyanobiphenyls (CBn) have been widely studied by different methods due to their readily accessible nematic ranges around room temperature. The compounds have the phase sequences crystal-nematic-isotropic for CBS, CBIO, and monotropic nematic for CBS, CB4 crystal-smectic A-nematic-isotropic for CB9 crystal-smectic A-isotropic for CBll. The lower homologous CB2 is nonmesogenic. The general chemical structure of the compounds CBn is presented in Fig. 1. 

The liquid crystalline state may be identified as a distinct and unique state of matter which is characterised by properties which resemble those of both solids and liquids. It was first recognised in the middle of the last century through the study of nerve myelin and derivatives of cholesterol. The research in the area really gathered momentum, however, when as a result of the pioneering work of Gray in the early 1970 s organic compounds exhibiting liquid crystalline properties were shown to be suitable to form the basis of display devices in the electronic products. 

Liquid-crystalline complexes (metallomesogens) containing platinum(II) are new types of materials that have been the subject of several studies. These have largely included complexes of the type trans-[PtX2L2] (X = C1, L = cyanobiphenyls 229 X = C1, carboxylate, L = 4-alkoxy-4 stilbazoles 230 X = C1, L = 2,4-, 3,4-, or 3,5-dialkoxystilbazoles, 2,3,4-, 2,4,5-, or 3,4,5-trialkoxystilbazoles).231,232 Their liquid-crystalline properties have also been reported. 

Mesomorphic dendrimers containing electroactive units have potential for construction of dendrimer based molecular switches. Deschenaux et al. reported [154] the synthesis and liquid-crystalline properties of a novel dendrimer containing six mesomorphic ferrocene units. Apart from exhibiting a broad enantiotropic smectic A phase as determined by polarized optical microscopy, DSC, and XRD studies, thermogravimetry revealed the excellent thermal stability of the macromolecule. 

Polyisocyanates have attracted much attention owing to their liquid crystalline properties, stiff-chain solution characteristics, and induced optical activities associated with helical chain conformation (Scheme 8). Pattern and Novak [39]... 

Acetals of L-galactono-1,4-lactone (an abundant byproduct of the sugar beet industry) have thermotropic liquid crystalline properties. Acetalization in DMF containing H2S04 in the presence of anhydrous CuS04 gave (after 12 to 24 h at 40 °C) yields of 20-35% (Scheme 8.27). 

G.S. Attard, P.N. Bartlett, N.R.B. Coleman, J.M. Elliott, and J.R. Owen, Lyotropic liquid crystalline properties of nonionic surfactant/H20/hexachloroplatinic acid ternary mixtures used for the production of nanostructured platinum. Langmuir 14, 7340-7342 (1998). 

The first reports on the liquid crystalline properties of pyramidal or cone-shaped materials appeared in 1985.65 It was discovered that compounds with... 

Size and shape Certain steric effects can be achieved using characteristically wedge-shaped dendrons. Thus, self-assembling dendrons have been connected to supramolecular aggregates with defined dimeric or hexameric structures. Such aggregates can form columnar superstructures which reveal liquid-crystalline properties. Spherical superstructures arise from the self-assembly process when conical dendrons are used14 14,161 Similar... 

Thermotropic liquid crystalline (LC) phases or mesophases are usually formed by rod-like (calamitic) or disk-like (discotic) molecules. Spheroidal dendrimers are therefore incapable of forming mesophases unless they are flexible, because this would allow them to deform and subsequently line up in a common orientation. However, poly(ethyleneimine) dendrimers were reported to exhibit lyotropic liquid crystalline properties as early as 1988 [123],... 

Totally synthetic bilayers show liquid crystalline properties similar to those of lecithin bilayers (Nagamura et al., 1978 Kano et al., 1979). Bilayer formation has also been observed for dialkyl compounds with anionic head groups such as [2] and [3] (Kunitake and Okahata, 1978a Mortara et al., 1978), and with nonionic and zwitterionic head groups as in [4] and [5] (Okahata et al., 1978a). 

Kim reported on liquid crystalline properties observed for hyperbranched aromatic amides obtained from 3,5-diaminobenzoic acid and derivatives thereof. The resulting polymers exhibited nematic liquid crystalline phases [89]. 

This transformation of alkyl 2-chloro-2-cyclopropylideneacetates has been applied for the preparation of compounds of type 83 containing a czs-configurated disubstituted cyclopropane moiety [25] with potential liquid crystalline properties [52]. In the first approach to such compounds, 2-chloro-2-cyclopropylide-neacetic acids 2b-H, 2i-H were coupled with the linear diaryl components 81 fol-... 

Scheme 21. Preparation of biaryl derivatives of type 83 with potential liquid crystalline properties from 2-chloro-2-cyclopropylideneacetic acid. Conditions A DCC, CH2CI2, 0°C, 5 h. B DEAD, Ph3P, Et20,20°C, 14 h [25]...

As compared to the cholesteric LC, the lyotropic LC consists of two or more components that exhibit liquid-crystalline properties (dependent on concentration, temperature, and pressure). In the lyotropic phases, solvent molecules fill the space around the compounds (such as soaps) to provide fluidity to the system. In contrast to thermotropic liquid crystals, these lyotropics have another degree of freedom of concentration that enables them to induce a variety of different phases. A typical lyotropic liquid crystal is surfactant-water-long-chain alcohol. 

Acyclic carbohydrates with two alkyl chains have been studied in detail in the case of dialkyldithioacetals 9. It is one of the more complete series whose results have been cross-checked and compiled [43]. Their liquid crystalline properties were compared with those of dodecyl a- and -D-glucofuranosides [50] depending on their structures, they form either hexagonal disordered columnar phases or a new rectangular columnar phase [77]. 

Hexahydrofuro[2,3- ]pyrai derivatives react with phenols to produce ether and ester derivatives in excellent yields (Equation 10) <1999EJ02429>. Several of these compounds exhibit liquid crystalline properties. 

In many cases, these polymer chains take on a rod-like (calamitic LCPs) or even disc-like (discotic LCPs) conformation, but this does not affect the overall structural classification scheme. There are many organic compounds, though not polymeric in nature, that exhibit liquid crystallinity and play important roles in biological processes. For example, arteriosclerosis is possibly caused by the formation of a cholesterol containing liquid crystal in the arteries of the heart. Similarly, cell wall membranes are generally considered to have liquid crystalline properties. As interesting as these examples of liquid crystallinity in small, organic compounds are, we must limit the current discussion to polymers only. 

Figure 39 represents schematically such a process in the case of two-site (ditopic) complementary components Te 2 and Ts2. The resulting supramolecular polymeric material ((Te 2, T32) may present liquid-crystalline properties if suitable chains are grafted onto the components. One may note that the mixed site species e Tsrepre-... 

A feature of most cancer cells is that they exhibit a disturbance of the ordered structures and biological regulation observed in normal cells. Evidence is presented, based on studies of living cells and on electron microscopy, which indicates that the arrangement of molecules within the plasma membrane and of subsurface microfilaments has certain properties that are similar to those of liquid crystals. These liquid crystalline properties are disturbed in malignant cells. 

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