Lyotropics chiral

A statistical model was introduced by Ki-mura et al. [25] which included attractive and repulsive asymmetric intermolecular forces for rod-like molecules. The results are summarized as Eq. (5), which is widely used for the lyotropic chiral nematic state... 

Only a few solvents are known to dissolve cellulose completely, and solid cellulose decomposes before melting. Therefore, it is difficult to study the mesophase behavior of cellulose. Chanzy et al. [32] reported lyotropic mesophases of cellulose in a mixture of jV-methyl-morpholine-Af-oxide and water (20-50%), but were unable to determine the nature of the mesophase. Lyotropic cholesteric mesophase formation in highly concentrated mixtures of cellulose in trifluoroa-cetic acid + chlorinated-alkane solvent [33] and in ammonia/ammonium thiocyanate solutions [34] has been studied, and although poor textures were obtained in the polarizing microscope, high optical rotatory power has been measured in an optical rotation (ORD) experiment, which could be fitted to the de Vries equation [Eq. (3)] for selective reflection beyond the visible wavelength region and was taken as proof of a lyotropic chiral nematic phase. 

At very low concentrations, these nanocrystals are randomly suspended in water and form an isotropic phase. When the concentration reaches a critical value, the nanocrystals spontaneously display ordered phases showing interesting lyotropic chiral nematic liquid crystalline (N -LC) phase [21]. 

Zhang, D., Zhang, L., Wang, B., and Piao, G. (2013). Nanocomposites of pol3 niline and cellulose nanociystals prepared in lyotropic chiral nematic liquid crystals, J. Mater., 2013, Article ID 614507, 6 pp. http //dx.doi.org/10.1155/2013/614507. 

B.A. San Jose, S. Matsushita, K. Akagi, Lyotropic chiral nematic liquid crystalline aliphatic conjugated polymers based on di-substituted polyacetylene derivatives that exhibit high dissymmetry factors in circularly polarized luminescence. J. Am. Chem. Soc. 134, 19795-19807 (2012)... 

J.R. Bruckner, J.H. Porada, F. Knecht, C.F. Dietrich, M. Harjung, F. Giesselmann, Lyotropic chiral smectic C liquid crystal with polar electro-optic switching, 25th International Liquid Crystal Conference (CL-02.001), Dublin, Ireland, (2014)... 

The course of versus x becomes nonlinear at elevated dopant concentrations mostly the absolute value of the slope deceases but some exceptions are known [23]. For a few cases a maximum twist has been found, especially when a lamellar phase is adjacent to the chiral nematic one. Then pretransitions obviously occur close to the lamellar state, as has been shown already in the basic paper by Radley and Saupe [9], [24]. So far, lyotropic chiral nematics seem to behave quite similar to their thermotropic counterparts. 

Together with the report on the discovery of lyotropic chiral nematics, the very first proposals for mechanisms of chiral interaction were published by Radley and Saupe [9]. The authors discussed two models ... 

Reeves et al. argued that a dispersion type of interaction between single chiral molecules in adjacent micelles is rather imlikely to be essential for the phase chirality [35], Dispersion interactions between colloidal particles, as well as between single molecules, decrease with a strong power of the interparticle distance d (by d to d ). In thermotropic cholesteric or chiral smectic phases the interparticle distance is of the order of 100 pm which is small compared to the typical values of 1 to 10 nm between micelles in lyotropic chiral nematic phases. 

In conclusion, electric field effects in liquid crystals is a well-developed branch of condensed matter physics. The field behavior of nematic liquid crystals in the bulk is well understood. To a certain extent the same is true for the cholesteric mesophase, although the discovery of bistability phenomena and field effects in blue phases opened up new fundamental problems to be solved. Ferroelectric and antiferroelectric mesophases in chiral compounds are a subject of current study. The other ferroelectric substances, such as discotic and lyotropic chiral systems and some achiral (like polyphilic) meso-genes, should attract more attention in the near future. The same is true for a variety of polymer ferroelectric substances, including elastomers. 

Licjuid Crystals. Ferroelectric Hquid crystals have been appHed to LCD (Uquid crystal display) because of their quick response (239). Ferroelectric Hquid crystals have chiral components in their molecules, some of which are derived from amino acids (240). Concentrated solutions (10—30%) of a-helix poly(amino acid)s show a lyotropic cholesteric Hquid crystalline phase, and poly(glutamic acid ester) films display a thermotropic phase (241). Their practical appHcations have not been deterrnined. 

Many cellulose derivatives form Hquid crystalline phases, both in solution (lyotropic mesophases) and in the melt (thermotropic mesophases). The first report (96) showed that aqueous solutions of 30% hydroxypropylceUulose [9004-64-2] (HPC) form lyotropic mesophases that display iridescent colors characteristic of the chiral nematic (cholesteric) state. The field has grown rapidly and has been reviewed from different perspectives (97—101). 

The mixing of nematogenic compounds with chiral solutes has been shown to lead to cholesteric phases without any chemical interactions.147 Milhaud and Michels describe the interactions of multilamellar vesicles formed from dilauryl-phosphotidylcholine (DLPC) with chiral polyene antibiotics amphotericin B (amB) and nystatin (Ny).148 Even at low concentrations of antibiotic (molar ratio of DLPC to antibiotic >130) twisted ribbons are seen to form just as the CD signals start to strengthen. The results support the concept that chiral solutes can induce chiral order in these lyotropic liquid crystalline systems and are consistent with the observations for thermotropic liquid crystal systems. Clearly the lipid membrane can be chirally influenced by the addition of appropriate solutes. 

Chiral Lyotropic Discotic Liquid Crystals and Self-Assembly of Chiral Discotics in Dilute Solution... 

Reinitzer discovered liquid crystallinity in 1888 the so-called fourth state of matter.4 Liquid crystalline molecules combine the properties of mobility of liquids and orientational order of crystals. This phenomenon results from the anisotropy in the molecules from which the liquid crystals are built. Different factors may govern this anisotropy, for example, the presence of polar and apolar parts in the molecule, the fact that it contains flexible and rigid parts, or often a combination of both. Liquid crystals may be thermotropic, being a state of matter in between the solid and the liquid phase, or they may be lyotropic, that is, ordering induced by the solvent. In the latter case the solvent usually solvates a certain part of the molecule while the other part of the molecule helps induce aggregation, leading to mesoscopic assemblies. The first thermotropic mesophase discovered was a chiral nematic or cholesteric phase (N )4 named after the fact that it was observed in a cholesterol derivative. In hindsight, one can conclude that this was not the simplest mesophase possible. In fact, this mesophase is chiral, since the molecules are ordered in... 

CHIRAL LYOTROPIC DISCOTIC LIQUID CRYSTALS AND SELF-ASSEMBLY OF CHIRAL DISCOTICS IN DILUTE SOLUTION... 

Several natural10 and synthetic (e.g., polyisocyanates11) polymers form lyotropic cholesterics with the appropriate solvent also micellar systems formed by amphiphilic molecules and water, if chirality is introduced by either using a chiral amphiphile or adding a chiral dopant, can give cholesteric phases.12... 

In this report, we have summarized some attempts to correlate molecular to cholesteric chirality both in thermotropic and lyotropic fields. In the former case, we have described only cholesteric induction, while in the lyotropic field, only cholesterics formed by helical polymers have been dealt with, as chiral micellar systems, for the moment, are too complex. 

Lyotropic polymeric LC, formed by dissolving two aromatic polyamides in concentrated sulphuric acid, have been studied using variable-director 13C NMR experiments.324 The experimental line shapes at different angles w.r.t the external field were used to extract macromolecular order and dynamic in these ordered fluids. An interesting application of lyotropic LC is for the chiral discrimination of R- and S-enantiomers, and has recently been demonstrated by Courtieu and co-workers.325 The idea was to include a chiral compound 1-deutero-l-phenylethanol in a chiral cage (e.g., /1-cyclodextrin) which was dissolved and oriented by the nematic mean field in a cromolyn-water system. Proton-decoupled 2H NMR spectrum clearly showed the quad-rupolar splittings of the R- and S-enantiomers. The technique is applicable to water-soluble solutes. 

These schemes have been frequently suggested [105-107] as possible mechanisms to achieve the chirally pure starting point for prebiotic molecular evolution toward our present homochiral biopolymers. Demonstrably successftd amplification mechanisms are the spontaneous resolution of enantiomeric mixtures under race-mizing conditions, [509 lattice-controlled solid-state asymmetric reactions, [108] and other autocatalytic processes. [103, 104] Other experimentally successful mechanisms that have been proposed for chirality amplification are those involving kinetic resolutions [109] enantioselective occlusions of enantiomers on opposite crystal faces, [110] and lyotropic liquid crystals. [Ill] These systems are interesting in themselves but are not of direct prebiotic relevance because of their limited scope and the specialized experimental conditions needed for their implementation. 

Note 5 If the mesogenic side-groups are rod-like (calamitic) in nature, the resulting polymer may, depending upon its detailed structure, exhibit any of the common types of calamitic mesophases nematic, chiral nematic or smectic. Side-on fixed SGPLC, however, are predominantly nematic or chiral nematic in character. Similarly, disc-shaped side-groups tend to promote discotic nematic or columnar mesophases while amphiphilic side-chains tend to promote amphiphilic or lyotropic mesophases. 

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