Infrared Rotatory Dispersion of Liquid-Crystalline Solutions of Chiral Molecules

1977 ◽  
Vol 16 (11) ◽  
pp. 790-791 ◽  
Author(s):  
Ernst-Heiner Korte ◽  
Bernhard Schrader ◽  
Sauvarop Bualek ◽  
Hans Jürgen Krabbe
Keyword(s):  
Liquid Crystalline ◽  
Rotatory Dispersion ◽  
Chiral Molecules

Discrimination of Enantiomers at Microgram Level Using Liquid Crystalline Solutions

1978 ◽  
Vol 32 (6) ◽  
pp. 568-572 ◽  
Author(s):  
E. H. Korte
Keyword(s):  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Liquid Crystalline ◽  
Dispersion Curves ◽  
Rotatory Dispersion ◽  
Chiral Molecules ◽  
Low Concentration ◽  
Infrared Spectrometer

In a nematic liquid crystal a cholesteric, i.e., helical, arrangement of molecules is induced by doping with a low concentration of chiral molecules. This structure is oppositely coiled for enantiomers leading to countercurrent infrared rotatory dispersion curves. It is shown that by employing this effect, enantiomers can be discriminated even if only microgram quantities are available. The measurement of the rotatory dispersion using a normal infrared spectrometer is described, and examples to demonstrate the applicability are given.

scholarly journals Cubic and tetragonal liquid crystal phases composed of non-chiral molecules: Chirality and macroscopic properties

2019 ◽  
Vol 42 (11) ◽  
Author(s):  
Helmut R. Brand ◽  
Harald Pleiner
Keyword(s):  
Liquid Crystal ◽  
Liquid Crystalline ◽  
Triblock Copolymers ◽  
Similar Type ◽  
Chiral Molecules ◽  
Chiral Compounds ◽  
Liquid Crystalline Phases ◽  
Symmetry Properties ◽  
Crystal Phases ◽  
Liquid Crystal Phases

Abstract. We discuss the symmetry properties as well as the macroscopic behavior of the cubic liquid crystal phases showing large chiral domains of either hand in some non-chiral compounds reported recently in the group of Tschierske. These phases are tricontinuous. While they have O or I432 symmetry in each chiral domain, the overall symmetry is $ I m \bar{3} m$Im3¯m as there is no net chirality for compounds composed of non-chiral molecules. It turns out that a rather similar type of phase has also been reported for triblock copolymers. Here we analyze in detail the macroscopic static and dynamic behavior of such phases and we predict, among other results, that they show the analog of static and dissipative Lehmann-type effects in their chiral domains. A description of a cubic liquid crystalline phase of Th symmetry, which has not yet been found experimentally, is also included. Suggestions for experiments are outlined to identify such a phase. In addition, we discuss tetragonal liquid crystalline phases of D4h and D4 (I422) symmetry as they have been reported last year experimentally in connection to the Q phase. Graphical abstract

Reactive Mesogenes: Synthesis and Application in Optoelectronic Devices

2001 ◽  
Vol 709 ◽  
Author(s):  
Peter Strohriegl ◽  
Doris Hanft ◽  
Markus Jandke ◽  
Thomas Pfeuffer
Keyword(s):  
Liquid Crystalline ◽  
Room Temperature ◽  
Polymer Networks ◽  
Optoelectronic Devices ◽  
Chiral Molecules ◽  
Glass Forming ◽  
Writing Beam ◽  
Crystalline Core ◽  
Crosslinked Networks ◽  
The Stability

ABSTRACTReactive mesogenes posess polymerizable groups attached to a rigid, liquid crystalline core. From such molecules, densely crosslinked networks in which the liquid crystalline order is permanentely fixed can be formed by photopolymerization.Our major synthetic goal was the formation of glass forming reactive mesogenes. Such compounds do not crystallize upon cooling but vitrify and form supercooled LC-phases ('LC-glasses'). They exhibit broad LC-phases and enable us to carry out photopolymerization in a broad range of temperatures.We have systematically investigated how the topology of the reactive mesogenes influences the stability of the resulting glasses. Comparing twin molecules with three- and four-armed stars we found that the supercooled LC-phase in the three-armed stars has a stability superior to both twin molecules and four-armed stars. In the three-armed star Triple-4 with a suitable substituent pattern the supercooled LC-phase is stable at room temperature for at least nine months. Doped with suitable chiral molecules the glass forming nematics form cholesteric phases which were used for cholesteric polymer networks and for polarization holograms with one s-and one p-polarized writing beam.Furthermore we have extended our synthetic efforts to reactive mesogenes with three or five conjugated fluorene units as LC-core. After orientation, the mesogenes were photocrosslinked and used as active layer in OLEDs that emit highly polarized blue light.

Computer Simulation of Chiral Liquid Crystal Phases IX. Chiral Induction in Guest-host Systems - Calculation of the Helical Twisting Power

1999 ◽  
Vol 54 (12) ◽  
pp. 747-754 ◽  
Author(s):  
Reiner Memmer ◽  
Folkert Janssen
Keyword(s):  
Liquid Crystalline ◽  
Dopant Concentration ◽  
System Size ◽  
Chiral Molecules ◽  
Cholesteric Phase ◽  
Chiral Induction ◽  
Chiral Liquid Crystal ◽  
Liquid Crystalline Phases ◽  
Helical Twisting Power

Abstract The chiral induction in liquid crystalline phases was studied by Monte Carlo simulation of the chiral Lebwohl-Lasher model. Binary guest-host systems composed of achiral and chiral molecules as well as of different chiral molecules were investigated in dependence on the composition. A cholesteric phase was induced by dissolving a small fraction of chiral molecules in a nematic phase. For dilute solutions the equilibrium pitch was found to be a linear function of the chiral dopant concentration. Independent of system size effects the application of self-determined boundary conditions enabled the determination of the symmetry adapted quantities for the chiral induction, the helical twisting power (HTP) and the achiral helical twisting power (AHTP). Additionally, a different orientational behaviour of enantiomeric dopants in the chiral surroundings of a cholesteric host phase has been determined.

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