Effect of Crowding Agent Polyethylene Glycol on Lyotropic Chromonic Liquid Crystal Phases of Disodium Cromoglycate

Abstract

Adding crowding agents such as polyethylene glycol (PEG) to lyotropic chromonic liquid crystals (LCLCs) formed by water dispersions of materials such as disodium cromoglicate (DSCG) leads to a phase separation of the isotropic phase and the ordered phase. This behavior resembles nanoscale condensation of DNAs but occurs at the microscale. The structure of condensed chromonic regions in crowded dispersions is not yet fully understood, in particular, it is not clear whether the condensed domains are in the nematic (N) or the columnar (C) state. In this study, we report on small angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) measurements of mixtures of aqueous solutions of DSCG with PEG and compare results to measurements of aqueous solutions of pure DSCG. X-ray measurements demonstrate that addition of PEG to DSCG in the N phase triggers appearance of the C phase that coexists with the isotropic (I) phase. Within the coexisting region, the lateral distance between the columns of the chromonic aggregates decreases as the temperature is increased.

Shear-induced polydomain structures of nematic lyotropic chromonic liquid crystal disodium cromoglycate

“…The intensity at a constant azimuthal angle  is integrated over the momentum transfer range  m qq with m q being the momentum transfer value corresponding to the maximum intensity and q is taken as the half-width at half maximum of the intensity vs q peaks. In the experiments, 𝑞 𝑚 ≃ 0.13 Å −1 corresponds to the lateral distance ∼ 4.8 nm between the DSCG aggregates that is noticeably larger than the diameter ∼ 3.2 nm of the aggregates, in agreement with the previous studies 69,71,72,74 ; the reason is that the DSCG aggregates are separated by water, as schematically illustrated in Fig. 1b.…”

“…The LC PolScope relies on a monochromatic illumination of the wavelength  =546 nm and represents a liquid crystal slab that changes optical retardance under an applied electric field. Once the image is taken for a few different settings of the compensator, numerical analysis allows the unit to map the optical retardance  of the sample in the range (0 -273) nm and the in-plane orientation of the optical axis n X-ray diffraction is widely used to characterize LCLCs in equilibrium [68][69][70][71][72][73] . It is expected that rheological small-angle x-ray scattering (rheo-SAXS) and rheological wide-angle x-ray scattering (rheo-WAXS) could also provide an excellent insight into the structure under the shear flows.…”

Toroidal nuclei of columnar lyotropic chromonic liquid crystals coexisting with isotropic phase

“…In condensates with a fixed at c = 0.34 mol/kg, addition of PEG at concentration C > 0.011 mol/kg causes phase separation into the Col and I phases, as confirmed by X-ray measurements [20]. The Col inclusions are toroids with cross-sections resembling hexagons, Fig.…”

“…At T=45 • C , the solution remains in the I phase when c ≤0.40 mol/kg (≤17wt%); above this concentration, the Col and I phases coexist. The liquid crystalline regions exhibit a higher DSCG concentration compared to the overall concentration in the entire sample [6,32,33,20]. Fig.…”

A High-Resolution Terahertz Electric Field Sensor Using a Corrugated Liquid Crystal Waveguide

“…On the other hand, there have been many reports in recent years on nematic liquid crystals (LCs) [26,27], which are very sensitive to aspects of the external environment such as lights [28], electric fields [29], magnetic fields [30], and temperature [31][32][33]. Wang et al proposed an optical temperature sensor based on a silicon nitride micro-ring resonator incorporating LC cladding [34].…”