Cyanobiphenyl derivatives

Note Examples are potassium salts of unbranched alkanoic acids, lecithin, certain polyisocyanates, cellulose derivatives with side-chains, such as (2-hydroxypropyl)cellulose, and cyanobiphenyl derivatives of alkyl(triethyl)ammonium bromide. 

Since the cyanobiphenyl derivatives had proved to be excellent materials for electro-optic displays, equivalent homopolymer poly-siloxane liquid crystals, based on these low molar mass mesogens, were synthesized. Their properties are summarized in Table 1. Since the homopolymers only exhibited smectic phases, copolymers were prepared using destabilizing 2-methyl-substituted ester side-groups. As shown in Table 2, at sufficiently high ester-group concentrations, a... 

A549 Lung Cancer Cell Growth Inhibition Effect of a Cyanobiphenyl Derivative... 

Fig. 11.32 Inhibition of cell proliftaatirai by each cyanobiphenyl derivative I-n at a concentratirai of 5 tM in A549 human lung cancer cell lines for 96 h. Cell viability was expressed as a percentage relative to solvent (DMSO)-treated control incubatirais...

Table 3. Crystal and molecular data of mesogenic 4C(hydroxy-l-n-alkoxy)-4-cyanobiphenyls (CBO(CH2)nOH) and some derivatives... 

One alternative approach is to use photoisomerisable chiral compounds where the E and Z isomers have different helical twisting powers, e.g. menthone derivatives. By incorporating co-polymers, prepared from menthone containing monomers and cyano esters (5.5), as dopants into nematic LC mixtures materials, e.g. a mixture of cyanobiphenyls and cyanoterphenyls (E7 available from Merck), colour change can be effected by irradiating with UV light (365 nm). The colour obtained is dependent... 

As the formation of LC phase in comb-like polymers is predetermined by the interaction of mesogenic groups, it would have seemed, that the temperature range of LC state for such systems should not depend on the length of the main chain, i.e. on the degree of polymerization (DP). However, studies 44,49) on the dependence of Tc] on DP carried out for some polyacrylic and polymethacrylic derivatives of cyanobiphenyl, as well as for polyparabiphenylacrylate 51 (Fig. 5), have shown that... 

Derivatives of Biphenyl. By coupling diazo compounds and N-nitrosoacetyl derivatives obtained from substituted anilines with benzene, a large variety of biphenyl derivatives can be prepared in which only one of the rings is substituted. In this manner, the isomeric monosubstituted biphenyls, RCel CeHs, have been prepared in which R = Br, Cl, CH3, OCH3, NO2, CN, etc. The meta derivatives, such as 3-brQmobiphenyl (I), 3-nitrobiphenyl (II), and 3-cyanobiphenyl (III), are of particular interest because they cannot be prepared readily from biphenyl. The usefulness of the methods for the preparation of compounds of definite... 

Our group investigated the influence of the spacer length of 2,3-disubsti-tuted norbornene derivatives with cyanobiphenyl-mesogenic units [42] and with methoxybiphenyl-mesogenic units [43] on the mesophases. Exo,endo-his-[(4 -cyanobiphenyl-4-yl)oxy-n-alkyl]norborn-5-ene-2,3-dicarboxylates with different alkyl spacer lengths (IV-n, n=2-12) were synthesized in a straightforward manner. 

Ungerank et al. investigated the influence of different molybdenum Schrock-type initiators 1, 2 and 3 (see Fig. 2) on the polymerization of ( )- and (-)-exo,e tdo-bis[4 -cyanobiphenyl-4-yl)oxyalkyl]norborn-5-ene-2,3-dicarboxy-lates [( )-IV-n and (-)-IV-n] [47]. The initiator had a strong influence on the Z/E ratio of the double bond in the polymer chain and therefore also on the tacticity of the polymer chain. Using racemic 2,3-disubstituted norbornene derivatives, such as ( )-IV-n, the two adjacent monomers (diads) can in principle form eight different stereoisomers, as depicted in Fig. 5 [48]. 

In this chapter we want to discuss the correlation of the mesophase behavior of a cyanobiphenyl-based SCLCP with its backbone structure. As shown before, the backbone structure, the spacer lengths, and the mesogen density per repeat unit have great influence on the LC mesophase evolved. Ligure 8 shows some examples of backbone structures bearing the cyanobiphenyl-moiety that have been reported in literature. The above-mentioned ROMP-derived polymers poly-(II-n) [39],poly-(IV-n) [42,47],poly-(VI-n) [41],andpoly-(VII-n) [53] will be compared with each other and with acrylate-based [56-59], siloxane-based [60] and vinylcyclopropane-based systems [61]. The detected mesophases and their transition temperatures are summarized in Table 6. 

Terunuma and coworkers reported the properties of a different type of carbosilane dendrimer (Nq = 3, Wb = 3) bearing either cyanobiphenyl species or an optically active unit derived from 2-phenylpyrimidine at the periphery (Fig. 15). Only three branches emanated from the central silicon atom, the fourth valency being blocked by a phenyl group leading to 3 (GO), 9 (Gl), and 27 (G2) terminal functional units. 

Excimer Formation of Cyanobiphenyls in a Calix[4]resorecinarene Derivative... 

Fig. 8 The structure of the ureidopyrimidinone (Upy) end-capped, pendant iptecene poly(p-phenylene ethylene) derivative (10) prepared by Hoogboom and Swager [72] to investigate alignment in the liquid crystal 4-n-pentyl-4 -cyanobiphenyl (5CB)...

In addition to toluene higher condensed methyl aromatic compounds and biphenyl derivatives, e. g. 1-methylnaphthaIene (on Cu-Na-mordenite [36]) or p-methylbiphenyl (to / -cyanobiphenyl and terephthalodinitrile [60]) can also be ammoxidized. The ammoxidation route can also be used to insert nitrogen into very highly condensed products, e. g. lignins [61,62], or active carbon [63]. 

Figure 24. Biomesogenic structures a) (Bio)meso-gens displaying order-disorder distributions in CPK-presentation (left to right and top to bottom) hexa-n-alkanoyl-oxybenzene discoid - Chandrasekar s first non-rodlike liquid crystal [28 a, 51c] enantiomeric cholesteric estradiol- and estrone-derivatives [ 17 a, c, d, 26 f, 51 a, s, u] Reinitzer s cholesterolbenzoate [21, 22] - together with the acetate the foundation stones of liquid crystal history [21, 22] Kelker s MBBA -first liquid crystal fluid at ambient temperature [ 13 f, g] Gray s cyanobiphenyl nematics for electrooptic displays [25 a, 51 e] lyotropic lecithin membrane component [7 a, 14, 27 d, 52 a] and valinomycin-K -membrane carrier [7 a, 35] thermotropic cholesteryl-side-chain-modifiedpolysiloxanes with the combination of flexible main-chain and side-chain spacers [51 a, h] thermotropic azoxybenzene polymers with flexible main-chain spacers [51a] thermotropic cya-...

Fig. 4.7. Relaxation time r for the fundamental twist fluctuation mode dots) as a function of sample thickness d. The aligning layer was rubbed Nylon, the liquid crystal was 4-n-pentyl-4 -cyanobiphenyl (5CB) in the nematic phase (T = 32° C). Comparison between the best fit of the theoretically derived equation (solid line) and the best fit assuming infinite anchoring strength (dashed line) is made [32].

The butyl derivative of these nickel complexes was investigated as a dye in a guest-host system using 4-pentyl-4 -cyanobiphenyl (5CB) as the host. The complex was found to have a large extinction coefficient of absorption (e = 28,000 moC dm cm at 860 nm) and dissolved in 5CB at concentrations up to 10% (w/w). At 20 °C, such solutions showed a dichroic ratio (Rd. defined as + /+x = absorbance) of 4.97 and a dye order parameter of 0.57. 

Here, we synthesized liquid crystalline PMP derivatives by introducing phen-ylcyclohexyl (PCH) or cyanobiphenyl (CB) LC groups into the side chains and macroscopically aligned the polymers in LC phases using a magnetic field of 12 T [13]. Poly-2 (Mn = 8,400) has PCH side chains linked with flexible dodecam-ethylene chains via ester moieties. Poly-3 (M — 8,500), on the other hand, has a CB LC moiety in its side chain (Fig. 11.6). 

Fig. 11.6 Structures of the LC PMP derivatives, Poly-2 having a phenylcyclohexyl LC moiety and Poly-3 having a cyanobiphenyl LC moiety...

The expressions for the flexoelectric coefficients presented in this section are derived using the molecular-field approximation. Therefore, care should be taken in the description of nematic liquid crystals composed of strongly polar molecules. In such liquid crystal materials (for example, cyanobiphenyls) the flexoelectric coefficients may be strongly affected by the short-range dipole-dipole correlations, which are considered in the following section. 

Cyanobiphenyl (55) [148] and redox pendant groups such as ferrocene (56) [149], viologen (see Section 13.4.3) [150], and Tetrathiafulvalene [151] (see Section 13.4.1.1) cores have been grafted on hydroxymethyl-EDOT 45. A copolymer containing pendant ferrocene groups has been obtained by copolymeri2ation of 56 and another EDOT derivative [149]. 

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