Confined chromonics and viral membranes

Abstract

Recent work at the University of Pennsylvania on two distinct topics will be reviewed: (1) chromonic liquid confined to spherical and cylindrical cavities, the former with degenerate planar boundary conditions and the latter with both degenerate planar and homeotropic boundary conditions, and (2) a theory for membranes formed by filamentous viruses in water solution with depletants.

Instability of toroidal nematics

“…However, in a wide class of lyotropic liquid crystals, called chromonics, which have only recently been discovered and fully characterized [12], K 2 may be as small as one tenth the (almost common) value of K 1 and K 3 . This explains, at least heuristically, a number of recent puzzling experiments, which have shown an unexpected excess of twist deformation arising in the equilibrium textures [14][15][16][17][18] (see also the witty review [19]). Now, both excess of twist and smallness of K 2 are the leitmotifs of our paper.…”

“…where a(σ) is a real function of σ only. For (18) to obey the inequality | sin α| 1, a must be such that |a(σ)| 1 + ησ cos ψ for all ψ ∈ [0, 2π], whence it follows that…”

“…(see Appendix A.4 for more details). Enforcing in this context the divergence-free condition for n amounts to linearize (18) in a, which thus becomes…”

Sunset Yellow Confined in Curved Geometry: A Microfluidic Approach

“… 6 , 7 Unlike lyotropic LCs, LCLCs do not form micelles; rather, they stack up as linear aggregates, held together by noncovalent interactions, which lead to a self-assembled nematic phase or a columnar phase with a hexagonal arrangement possessing unique optical properties. 8 − 11 The weak interaction forces driving the self-assembled phase formation make LCLCs highly responsive to external stimuli (temperature, concentration, pH, ionic content, etc.) and geometric constraints, thus conferring them distinctive properties such as negative birefringence and a large anisotropy in the elastic constants.…”

“…Lyotropic chromonic liquid crystals are a special class of lyotropic LCs that are formed by anisotropic assemblies of water-soluble disk-shaped molecules that have an aromatic core surrounded by ionic groups. Among LCLCs, there are DNA and its bases, disodium cromoglycate (DSCG), a commonly used drug, and sunset yellow (SSY), a dye used in the food industry. , Unlike lyotropic LCs, LCLCs do not form micelles; rather, they stack up as linear aggregates, held together by noncovalent interactions, which lead to a self-assembled nematic phase or a columnar phase with a hexagonal arrangement possessing unique optical properties. − The weak interaction forces driving the self-assembled phase formation make LCLCs highly responsive to external stimuli (temperature, concentration, pH, ionic content, etc.) and geometric constraints, thus conferring them distinctive properties such as negative birefringence and a large anisotropy in the elastic constants.…”