Intercalation or external binding: How to torque chromonic Sunset Yellow

The reflection symmetry breaking observed in chromonic liquid crystals confined in different geometries, like tactoids, microspheres or capillaries, has been the focus of researchers in the last few years. Although the assembly mechanism that drives this behavior is common to most chromonic materials, the interface phenomena and the induced chirality are strongly dependent on the chromonic molecule itself. In this work, we report advances in understanding the supramolecular arrangement and induced chirality for the chromonic molecule Sunset Yellow and its interaction with salts and l-peptides. By means of optical microscopy, X-ray diffraction and atomic force microscopy, we demonstrate the rise of enhanced chirality in Sunset Yellow microspheres and propose an explanation of this phenomenon through two possible mechanisms: intercalation of the chiral dopant or binding. Our findings on the capability to control the delicate thermodynamic balance among chromonics, ions, chiral dopants, and water and its kinetics may open new perspectives for using these microspheres in optical and sensing applications.