Extremely small twist elastic constants in lyotropic nematic liquid crystals
Journal article, 2020

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.

nematic liquid crystals


lyotropic liquid crystals

light scattering



C. F. Dietrich

University of Stuttgart

Peter J. Collings

University of Pennsylvania

Swarthmore College

Thomas Sottmann

University of Stuttgart

Per Rudquist

Chalmers, Microtechnology and Nanoscience (MC2), Electronics Material and Systems

F. Giesselmann

University of Stuttgart

Proceedings of the National Academy of Sciences of the United States of America

0027-8424 (ISSN) 1091-6490 (eISSN)

Vol. 117 44 27238-27244

Subject Categories

Inorganic Chemistry

Physical Chemistry

Other Materials Engineering





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