ChemInform Abstract: INFRARED ROTATORY DISPERSION OF LIQUID CRYSTAL SOLUTIONS OF CHIRAL MOLECULES

1978 ◽  
Vol 9 (11) ◽  
Author(s):  
E.-H. KORTE ◽  
B. SCHRADER ◽  
S. BUALEK ◽  
H. J. KRABBE
Keyword(s):  
Liquid Crystal ◽  
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.

ON AN ORIENTATION TRANSITION IN NEMATIC LIQUID CRYSTALS INDUCED BY THE THICKNESS OF THE SAMPLE

1993 ◽  
Vol 07 (18) ◽  
pp. 1215-1222
Author(s):  
A. L. ALEXE-IONESCU
Keyword(s):  
Experimental Data ◽  
Phase Transitions ◽  
Liquid Crystal ◽  
Nematic Liquid Crystal ◽  
Tilt Angle ◽  
Critical Thickness ◽  
Large Range ◽  
Square Root ◽  
Chiral Molecules ◽  
Homeotropic Orientation

An orientation transition observed in nematic liquid crystal samples, induced by the thickness, is interpreted in a new way. By supposing that the nematic liquid crystal contains chiral impurities, it is shown that the homeotropic orientation is stable only for thicknesses smaller than a critical one, and is dependent on the concentration of the chiral molecules. At the critical thickness, the transition from the homeotropic orientation to the distorted one is characterized by a tilt angle proportional to the square root of the actual thickness minus the critical one. This trend is typical of second order phase transitions. The agreement between the theory and the experimental data is fairly good over a large range of thickness of the sample.

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

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
Sign in / Sign up

Export Citation Format

Share Document