LIQUID CRYSTALS NUCLEI COEXISTING WITH AN ISOTROPIC PHASE

Abstract

The morphology of finite-size condensed materials is influenced by surface tension. To reduce surface area, tiny droplets of water in the air have spherical shapes, but solid crystals have facetted shapes defined by the orientation dependency of surface tension. Bulk interactions are unimportant in these two examples because they are either too weak to overcome surface tension in the first case or too powerful to enable internal curvatures in the second case. In liquid crystal droplets, the bulk and surface energies are more closely balanced, resulting in a more diversified morphology of structures such as smectic "batonnets", nematic spindle-like tactoids, and even the possibility for droplet division . Liquid crystals are well-known examples of ordered materials whose nuclei emerge from an isotropic state and have a shape topologically equivalent to a sphere. In the first part of the thesis, we explore experimentally and theoretically the nuclei of columnar lyotropic chromonic liquid crystal coexisting with the isotropic phase that is toroidal in shape. We study the lyotropic chromonic liquid crystal (LCLC) composed by plank-like molecules of disodium chromoglycate (DSCG) with hydrophobic polyaromatic cores and hydrophilic peripheries. The goal is to establish the physical mechanisms in the balance of elasticity and anisotropic surface tension that produce toroidal shapes and establish how these shapes depend on parameters such as molecular concentrations and the presence of a crowding agents. The second part of the thesis will focus on the droplets of chiral and ferroelectric liquid crystal materials.