Form nematic phase

Disc-like molecules with a pentakis(phenylethynyl)phenoxy core commonly form nematic phases which can be strongly stabilized by the presence of only one... 

Figure 10.35 Dependence on inverse temperature of the viscosities in each of the orientations depicted in Fig. 10-28 for a ternary mixture of 73% (by weight) 7CB, 18% 80CB, and 9% 5CT that forms nematic phases at high and low temperature and has an intermediate range of smectic A phase. Ihe dashed line is an Arrhenius temperature-dependence for (From Bhattacharya and Letcher 1980, reprinted with permission from the American Physical Society.)...

This algorithm has been applied to calculate the thermal conductivity of a variant of the Gay-Beme fluid where the Lennard-Jones core has been replaced by a purely repulsive 1/r core [20]. Two systems were studied, one consisting of prolate ellipsoids with a length to width ratio of 3 1 and another one consisting of oblate ellipsoids with a length to width ratio of 1 3. The potential parameters are given in Appendix II. They both form nematic phases at high densities. 

Optical texture observations and X-ray investigations showed that the polyacrylate 41 PA 3 and the copolymer 45 (x=0.8) form nematic phases. The polymethacrylate 41 PMA 3 and the copoly ether 45 (x=0.55) display no liquid crystallinity at rest, but exhibit a virtual isotropic liquid-nematic transition a few degrees below Tg, as evidenced by miscibility studies. Copolyether 46 does not show any threaded or schlieren texture, which would be characteristic of a nematic. 

The first examples of end-to-end connected bent-core—rod couples and rod—bent-core—rod trimesogens incorporating a bent 3,5-diphenyl-l,2,4-oxadiazole core (Figure 12) have been synthesized and their LC phase behaviors studied (2012BJO472). AH compounds form nematic phases over wide temperature ranges, in some cases accompanied by additional nontHted (CybA) or tilted (SmC) mesophases at lower temperatures. 

While most LCPs form nematic phases, all of the textures observed with low molar mass liquid crystals have been observed in polymers. Because of the importance of nematic LCPs, the discussion of LC textures will focus on the nematic phase, with other textures being discussed in less depth. 

Liquid crystal copolyesters have been S5rnthesized [50-56] on the basis of -acetoxybenzoic acid, acetoxybisphenol, terephthalic acid and m-acetoxybenzoic acid by means of polycondensation in melt. All the copolyesters are thermotropic and form nematic phase. The t5rpes of LQPs of -oxybenzoic acid are given in Table 7.2. 

Fig. 5.1-2b). Here the orientation of the director does not apply to the whole medium but rather to a virtual layer. Perpendicular to this layer, the director follows a helix with a certain pitch. In the case of the blue phases, such a helical structure is formed not in one but in all three dimensions. Thus, highly complex arrangements, with chiral cubic symmetry in most cases, are generated. Not only rod-like but also disk-like molecules can form nematic phases. The discoid nematic phase is shown in Fig.5.1-2c. 

These dinuclear chlorobridged complexes formed nematic phases at about 200 °C at much higher temperature and in a narrower range than the free ligand. The role... 

Nematic states occur also in nonionic monomeric and polymeric surfactant solutions, living amoeboid cells i and rigid or semiflexible polymeric rods, such as fd virus in water solutions. - We note that colloidal suspension of semiflexible virus particles also form nematic phases. - ... 

X-ray crystal structure analysis is the most powerful and widely used method for structure determination in chemistry. A brief survey of the principles of the method [1] and the characteristic features of typical examples of crystal structures of mesogens that form nematic phases are given here. 

The phenylbenzoate copolymers with the anthraquinone dye form nematic phases which decrease with increasing content of the dye monomer as shown in Fig. 2. The copolymer with an anthraquinone monomer content of about 39 % by weight is no longer liquid crystalline. 

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