Induced Chiral Chromonics Confined in Micrometric Droplets

Abstract

Chirality emergence in biological systems is common but the chiral expression from the molecular to macroscopic level in water‐based systems is poorly understood. Among water‐based systems, chromonic liquid crystals have recently received a lot of attention due to the spontaneous chirality they show when confined in curved geometries. Confinement of chiral‐induced chromonics is not trivial since they are three component systems whose time stability is a delicate thermodynamic balance. In this work, a well‐defined periodic Frank–Pryce texture, typical of chiral thermotropic liquid crystals, is observed in microspheres of a chiral induced chromonic embedded in a poly(dimethylsiloxane) matrix. This texture slowly degrades in time and a possible mechanism behind the degradation process is suggested via X‐ray diffraction and atomic force microscopy measurements on thin chromonic films. To stabilize this texture and to control the structure periodicity, cations are added to the three components system in an attempt to tune the non‐covalent interactions between molecules and supramolecular stacks. The study of the effects of this addition allows for better insight into the molecular interactions that occur in the chiral induced mesophase. This is a crucial point in view of possible biocompatible technological applications.

Spherical Confinement of Chromonics: Effects of a Chiral Aminoacid

“…If refrigerated at 4 • C, the texture is preserved for two weeks. From previous observations [13] we have found that oxazine 725 improves the quality of the Frank-Price texture (Figure 4c and 4d). Figure 5c and Figure 5d show, in the case of DSCG containing L-alanine, that the number of microspheres with a well-defined texture increases when the material is doped with oxazine.…”

“…Chiral textures in microspheres are also easily measurable with a polarized-light optical microscope (POM), since in curved geometries, chirality is straightforwardly detectable, especially for high pitch values [12]. The textures observed in chromonics [13] are similar to the ones reported in several papers focused on chiral TLCs, even if LCLCs contain different ingredients that are thermodynamically balanced in the mesophases with respect to TLCs. Loss of water, temperature variations, changes in dopant solubility and the use of ions can affect the phase diagram and, consequently, the droplet state diagram [5].…”

“…Thin films of the chiral material are studied as well to obtain information on the chirality induction mechanism; the results confirm what has been previously observed for L-alanine-doped DSCG. In addition, in the case of Trans-Hyp, it appears clear that the mechanism involved in induced chirality is an external binding of the chiral molecules to DSCG cylinders [13]. Nevertheless, in the reported case, the presence of Trans-Hyp considerably increases the number of microspheres that exhibit the ordered texture.…”

“…As known from the literature, Trans-Hyp has a greater twisting power than L-alanine (0.75 μm −1 •wt% −1 for L-alanine and 2.5 μm −1 •wt% −1 for Trans-Hyp) [10,11]. Based on previous experience with emulsions of DSCG doped with L-alanine [13] the results presented in this paper indicate that the addition of the Trans-Hyp allows us to obtain a shorter pitch with respect to the one observed in L-alanine-doped samples. A well-defined Frank-Pryce structure is observed.…”

Effect of the degree of protonation of amino acid dopants in Chirality amplification in DSCG Lyotropic Nematic phases.

“…29 Very recently, chirality has also been induced in DSCG confined in spherical geometries within a matrix (as shown by the emergence of Frank-Pryce textures). 30 With the aim to further broaden the scope of the use of DSCG as a chiral amplification agent, we decided to study in detail the relationship between the structure of the dopant, particularly its molecular charge and protonation state, and the degree of chiral amplification observed. The chosen systems were selected on the bases of hydrophilicity, availability in their enantiomerically pure forms and of low molecular weight.…”