Related Experiment Video
Updated: Feb 26, 2026
06:24
High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal
Published on: October 31, 2019
6.9K
Chiral smectic-A and smectic-C phases with de Vries characteristics
Neelam Yadav1,2, V P Panov1, V Swaminathan1
1Department of Electronic and Electrical Engineering, Trinity College Dublin, University of Dublin, Dublin 2, Ireland.
Physical Review. E
|July 16, 2017
Summary
This study investigates chiral smectic liquid crystals using infrared and dielectric spectroscopy. Results confirm de Vries behavior and reveal insights into electro-optical responses and dipolar fluctuations in the Smectic-A* phase.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Physical Chemistry
Background:
- Chiral smectic liquid crystals exhibit complex electro-optical properties.
- Understanding molecular behavior in the Smectic-A* phase is crucial for device applications.
- The de Vries concept offers a framework for explaining certain liquid crystal phenomena.
Purpose of the Study:
- To investigate the characteristics of two specific chiral smectics (MSi3MR11 and W599).
- To analyze orientational features and field dependencies of tilt angle and dichroic ratio.
- To apply the generalized Langevin-Debye model to experimental data.
Main Methods:
- Infrared spectroscopy to analyze absorbance profiles and dichroic ratios.
- Dielectric spectroscopy to detect dipolar fluctuations.
- Variable temperature and electric field measurements.
Main Results:
- Low order parameters consistent with de Vries behavior were observed in the Smectic-A* phase.
- The generalized Langevin-Debye model effectively explained electro-optical responses.
- Dipolar fluctuations were significant in the Smectic-A* phase, confirming de Vries behavior.
Conclusions:
- The study confirms de Vries behavior in the investigated chiral smectics.
- The generalized Langevin-Debye model provides valuable insights into order parameters and dichroic ratios.
- Significant dipolar fluctuations in the Smectic-A* phase support the de Vries concept.
Related Concept Videos
02:05Prochirality
5.1K
The concept of prochirality leads to the nomenclature of the individual faces of a molecule and plays a crucial role in the enantioselective reaction. It is a concept where two or more achiral molecules react to produce chiral products. A typical process is the reaction of an achiral ketone to generate a chiral alcohol. Here, the achiral reactant reacts with an achiral reducing agent, sodium borohydride, to generate an equimolar mixture of the chiral enantiomers of the product. For example, an...
5.1K
02:33Stereoisomerism of Cyclic Compounds
11.3K
In this lesson, we delve into the role of ring conformation and its stability, which determines the spatial arrangement and, consequently, the molecular symmetry and stereoisomerism of cyclic compounds. 1,2-Dimethylcyclohexane is used as a case study to evaluate the possible number of stereoisomers. Here, given the multiple (n = 2) chiral centers, there are 2n = 4 possible configurations that lack a plane of symmetry, as the ring skeleton exists in a non-planar chair conformation. In addition,...
11.3K
02:25Chirality
30.4K
Chirality is a term that describes the lack of mirror symmetry in an object. In other words, chiral objects cannot be superposed on their mirror images. For example, our feet are chiral, as the mirror image of the left foot, the right foot, cannot be superposed on the left foot.
Chiral objects exhibit a sense of handedness when they interact with another chiral object. For example, our left foot can only fit in the left shoe and not in the right shoe. Achiral objects — objects that have...
Chiral objects exhibit a sense of handedness when they interact with another chiral object. For example, our left foot can only fit in the left shoe and not in the right shoe. Achiral objects — objects that have...
30.4K
01:16Thermal Sigmatropic Reactions: Overview
2.6K
Sigmatropic rearrangements are a class of pericyclic reactions in which a σ bond migrates from one part of a π system to another. These are intramolecular rearrangements where the total number of σ and π bonds remain unchanged.
Sigmatropic shifts are classified based on an order term [i, j ], where i and j indicate the number of atoms across which each end of the σ bond migrates. Below are examples of a [3,3] sigmatropic shift in 1,5-hexadiene, referred...
Sigmatropic shifts are classified based on an order term [i, j ], where i and j indicate the number of atoms across which each end of the σ bond migrates. Below are examples of a [3,3] sigmatropic shift in 1,5-hexadiene, referred...
2.6K
02:37Disubstituted Cyclohexanes: cis-trans Isomerism
14.7K
Depending upon the different spatial orientation of the substituents, the disubstituted cycloalkanes exhibit two types of stereoisomers. The cis isomers have the substituents on the same side of the ring, whereas the trans isomers have the substituents on the opposite sides. These stereoisomers exhibit different physical properties and cannot be interconverted without breaking the carbon-carbon bonds.
In cyclohexane, the substituents can occupy different positions generating distinct isomers....
In cyclohexane, the substituents can occupy different positions generating distinct isomers....
14.7K
![[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement](/_next/image?url=https%3A%2F%2Fcloudfront.jove.com%2Ffiles%2Fmedia%2Fscience-education%2Fscience-education-thumbs%2F12422.jpg&w=3840&q=75)
01:21[3,3] Sigmatropic Rearrangement of 1,5-Dienes: Cope Rearrangement
3.5K
The Cope rearrangement is classified as a [3,3] sigmatropic shift in 1,5-dienes, leading to a more stable, isomeric 1,5-diene. The reaction involves a concerted movement of six electrons, four from two π bonds and two from a σ bond, via an energetically favorable chair-like transition state.
3.5K