Molecular dynamics of dilute binary chromonic liquid crystal mixtures

Abstract

The spontaneous aggregation of binary mixtures of lyotropic chromonic liquid crystals (LCLCs) was investigated using atomistic molecular dynamics simulations. Equimolecular binary mixtures were simulated in a highly dilute regime using three LCLC mesogens, namely, Sunset Yellow FCF (SSY), disodium cromoglycate (DSCG) and Bordeaux dye (BD). The influence of their molecular shape, conformational flexibility and hydrogen bonding capability in the formation of aggregates was studied in detail. Stacking distance comparison, hydrogen bond distribution analysis and solvent accessible surface area calculations were performed along with molecular visualization. The mixtures exhibited three different molecular segregation modes where the number of mixed π–π stacks was minimized. Aggregation of chromonic binary mixtures depends strongly on mesogen cross-sectional area differences. However, the distribution of LCLC solubilizing groups and their H-bonding density formed around mixed stacks contributed significantly to achieving different mixture segregation patterns. Average stacking distances between π–π interactions were consistently seen to be around 0.34 nm. Mesogens with similar long axis molecular length and high hydrogen bonding capacity represent a likely choice for the preparation of chromonic binary mixtures. These findings contribute to the understanding of general aggregation rules for chromonic mesophases which are required for the design of novel chromonic supramolecular applications.