4-«-Hexyloxy-4 -cyanobiphenyl

Figure 1 Molecular structures of (A) 4 -(hexyloxy)-4 -cyanobiphenyl (60CB), (B) 2,3-naphthylene bis[2-fluoro-4-(4-dodecyloxybenzoyloxy)benzoate] (N(2,3)-F-012), and (C) 1.3-phenylene bis[4-(4-14-tetradecyloxyphenyl)iminomethyl benzoate] (P10-O-PIMB), with the atomic labeling as used in this chapter.

TABLE 2 The predicted probabilities of the eleven most common confmmers fw 4-hexyloxy-4 -cyanobiphenyl in the isotropic and nematic [diases. 

In FIGURES I, 2 and 3 we have collected the components of the diffusion tensor obtained for 4-pentyl-4 -cyanobiphenyl (5CB) [6], 4-pentyloxybenzylidene-4 -heptylaniline (50.7) [7] and 4-hexyloxy-4 -cyanobiphenyl (60CB) [8] as a function of temperature. In the figures a third diffusion constant Dr is reported in fact the deuterium NMR technique allows us to measure the relaxation times for the different lines corresponding to deuterium atoms at different locations in the molecule. In solving the diffusion equation then a third diffusion term Dr is included, describing the intmial... 

Fig. 6. Two conformations tgtgt and gtttg) of the alkyl chain of 4- -hexyloxy-4 -cyanobiphenyl restricted to a plane.

The Eleven Most Common Conformers Adopted by 4- -Hexyloxy-4 -cyanobiphenyl in the Nematic and Isotropic Phases Together with Their Statistical Weights, Expressed as Percentages, Calculated with XJkT =2-78, XJkT=0 2>% and EJkT= 1-36 ... 

Figure 1. Atomistic and molecular level models for rod-shaped (top) and disc-shaped (bottom) mesogens. Examples shown 4/-n-pentyl-4-cyanobiphenyl (5CB) (rod-shaped) and hexakis(n-hexyloxy)triphenylene (HAT6) (disc-shaped). (This figure is Reproduced from Ref. 16.)...

Flexocoefficients have also been obtained from the threshold voltages and wave numbers of electric field-induced flexoelectric instabilities (which are discussed in more detaii in Chapter 4 by Buka et al. ) for ClPbislOBB and for the molecule 4-((3-(4-(4-(decyloxy) benzoyloxy)benzoyloxy) phenylimino) methyl)-3-hydroxyphenyl 4-(6-(4 -cyanobiphenyl-4-yloxy)hexyloxy) benzoate (BCCB), which is a dimer composed of a calamitic and a BC molecule. In both cases the flexocoefficients were found to have the same order as that of calamities. 

Four liquid crystalline compounds were studied 4-/i-pentyl-4 -cyanobi-phenyl (5CB), 4-/z-octyl-4 -cyanobiphenyl (8CB), 4-/i-hexyloxy-4 -n-pentyl-a-cyanostilbene (HOPCS) and MBBA. All the compounds have the nematic phase in convenient temperature range, and, in addition, 8CB has the smectic A phase. Both 5CB and 8CB have positive dielectric... 

Shashidhar et al. [75] studied the influence of pressure on the SmA- (re-entrant) nematic and N-I phase boundaries of mixtures of 4-n-hexyloxy- and 4- -octyloxy-4 -cyanobiphenyl. The maximum pressure where the SmA and re-entrant nematic phase, respectively, still exist, decreases with increasing mole fraction, x, of the hex-yloxy homolog till at x 0.30 the SmA phase disappears. Just in this mole fraction region the slope of the N-I transition... 

Daoudi et al. [83] applied the thermodynamic approach equal Gibbs energy analysis to the pressure-composition phase diagrams of binary mixtures exhibiting reentrant phase behavior. Three different solution models are tested. The experimental data for the 4-n-hexyloxy- and 4-n-octyl-oxy-4 -cyanobiphenyl system are successfully described by the regular solution hypothesis. 

Fig. 10. The variation of the order parameter CD for each. methylene group along the alkyl chain for 4- -hexyloxy-di3-4 -cyanobiphenyl at two temperatures in the nematic phase. The solid lines show the order parameter profile predicted...

---