Related Experiment Video
Updated: Dec 5, 2025

High-Contrast and Fast Photorheological Switching of a Twist-Bend Nematic Liquid Crystal
Published on: October 31, 2019
Extremely small twist elastic constants in lyotropic nematic liquid crystals
Clarissa F Dietrich1, Peter J Collings2,3, Thomas Sottmann1
1Institute of Physical Chemistry, University of Stuttgart, 70569 Stuttgart, Germany.
Abstract:
Recent measurements of the elastic constants in lyotropic chromonic liquid crystals (LCLCs) have revealed an anomalously small twist elastic constant compared to the splay and bend constants. Interestingly, measurements of the elastic constants in the micellar lyotropic liquid crystals (LLCs) that are formed by surfactants, by far the most ubiquitous and studied class of LLCs, are extremely rare and report only the ratios of elastic constants and do not include the twist elastic constant. By means of light scattering, this study presents absolute values of the elastic constants and their corresponding viscosities for the nematic phase of a standard LLC composed of disk-shaped micelles. Very different elastic moduli are found. While the splay elastic constant is in the typical range of 1.5 pN as is true in general for thermotropic nematics, the twist elastic constant is found to be one order of magnitude smaller (0.30 pN) and almost two orders of magnitude smaller than the bend elastic constant (21 pN). These results demonstrate that a small twist elastic constant is not restricted to the special case of LCLCs, but is true for LLCs in general. The reason for this extremely small twist elastic constant very likely originates with the flexibility of the assemblies that are the building blocks of both micellar and chromonic lyotropic liquid crystals.
Related Concept Videos
Angle of Twist - Elastic Range
Relation between Poisson's ratio, Modulus of Elasticity and Modulus of Rigidity
Strain and Elastic Modulus
Circular Shafts - Elastoplastic Materials
As torque on the...
Spin–Spin Coupling Constant: Overview
Qualitatively, any spin plus-half nucleus polarizes the spins of its electrons to the minus-half state. Consequently, the paired electron in the hydrogen–carbon bond must...
Deformations in a Transverse Cross Section
As the material stretches, it expands or contracts in orthogonal directions to the load. This phenomenon varies...

