ChemInform Abstract: RELATION BETWEEN THE INFRARED ROTATORY DISPERSION OF LIQUID CRYSTAL SOLUTIONS OF CHIRAL MOLECULES AND THEIR ABSOLUTE CONFIGURATION

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

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