What a twist cell experiment tells about a quartic twist theory for chromonics

Abstract

The elastic theory of chromonic liquid crystals is not completely established. We know, for example, that for anomalously low twist constants (needed for chromonics) the classical Oseen- Frank theory may entail paradoxical consequences when applied to describe the equilibrium shapes of droplets surrounded by an isotropic phase: contrary to experimental evidence, they are predicted to dissolve in a plethora of unstable smaller droplets. We proposed a quartic twist theory that prevents such an instability from happening. Here we apply this theory to the data of an experiment devised to measure the planar anchoring strength at the plates bounding a twist cell filled with a chromonic liquid crystal; these data had before been interpreted within the Oseen-Frank theory. We show that the quartic twist theory affords a slightly better agreement with the experimental data, while delivering a larger value for the anchoring strength.