Emulsion of Aqueous-Based Nonspherical Droplets in Aqueous Solutions by Single-Chain Surfactants: Templated Assembly by Nonamphiphilic Lyotropic Liquid Crystals in Water

Abstract

Single-chain surfactants usually emulsify and stabilize oily substances into droplets in an aqueous solution. Here, we report a coassembly system, in which single types of anionic or non-ionic surfactants emulsify a class of water-soluble nonamphiphilic organic salts with fused aromatic rings in aqueous solutions. The nonamphiphilic organic salts are in turn promoted to form droplets of water-based liquid crystals (chromonic liquid crystals) encapsulated by single-chain surfactants. The droplets, stabilized against coalescence by encapsulated in a layer (or layers) of single chain surfactants, are of both nonspherical tactoid (elongated ellipsoid with pointy ends) and spherical shapes. The tactoids have an average long axis of ∼9 μm and a short axis of ∼3.5 μm with the liquid crystal aligning parallel to the droplet surface. The spherical droplets are 5-10 μm in diameter and have the liquid crystal aligning perpendicular to the droplet surface and a point defect in the center. Cationic and zwitterionic surfactants studied in this work did not promote the organic salt to form droplets. These results illustrate the complex interplay of self-association and thermodynamic incompatibility of molecules in water, which can cause new assembly behavior, including potential formation of vesicles or other assemblies, from surfactants that usually form only micelles. These unprecedented tactoidal shaped droplets also provide potential for the fabrication of new soft organic microcapsules.

Straining soft colloids in aqueous nematic liquid crystals

“…The observation that these shape transformations accompany the DSCG phase transition suggests that elastic stresses imparted by the LC drive the GUV elongation and that a key factor that controls the shapes of the GUVs is a strain-induced efflux of DSCG solution from the interior of the small GUVs. Here, we note that a prior study has documented that the addition of high concentrations [> 6% (wt/wt)] of surfactants to isotropic phases of DSCG [5.5% (wt/wt) DSCG solutions at room temperature] generated nematic domains (31). Additional reports describe that similarly high concentrations of nonamphiphilic molecules, such as poly(vinyl alcohol) (32), PEG (33), and spermine (33), condense DSCG solutions and lead to the formation of nematic and columnar phases.…”

Orientation of chromonic liquid crystals by topographic linear channels: multi-stable alignment and tactoid structure

“…Tactoids, which are generally elongated and pointed, Zeppelin-shaped droplets in N-I twophase mixtures, are often observed because of wide temperature ranges of phase coexistence of CLCs [17][18][19][20][21][22][23]. Network-like textures, called reticulated textures, form during the heating from N phase or cooling from I phase [5,6].…”

Stereochemical Control of Nonamphiphilic Lyotropic Liquid Crystals: Chiral Nematic Phase of Assemblies Separated by Six Nanometers of Aqueous Solvents

“…In particular, the molecular assemblies of nonamphiphilic molecules in water give rise to the traditionally called chromonic liquid crystals − consisting of hydrated assemblies of nonamphiphilic molecules aligned with a separation of 5–6 nm in water. , These molecular assemblies are remarkable considering the large volume of water, yet the liquid crystal properties are similar to conventional thermotropic liquid crystals with regard to birefringence and temperature dependence of phase transitions. , This unique molecular assembly also raises the question of how the molecular organizations are influenced by chiral dopants or chiral mesogens. For these lyotropic chromonic liquid crystals, if the chiral mesogens or added chiral dopants were to have an impact on the organization of the molecular assemblies, there must exist a mechanism for how each assembly is influenced by the chiral environment created by the neighboring assemblies 6 nm away.…”