Hierarchically Organized Systems Based on Liquid Crystalline Phases

Abstract

In this chapter, we present hierarchically organized nanostructures formed from lyotropic liquid crystalline (LC) phases. The nano-, micro-, and macroscopic structural hierarchy arises from the kinetic stability of various lyotropic phases dispersed in oilin-water (O/W) or water-in-oil (W/O) emulsions. When an O/W emulsion consists of a dispersion of LC nanoparticles stabilized by certain stabilizers, it is called an ISAsome, that is, an internally self-assembled particle. In contrast, when the water droplets are dispersed in a continuous film of LC nanostructures, they are called W/O-nanostructured emulsions, which do not require a stabilizing agent. Both emulsions exhibit fascinating properties that can be tuned to a great extent. Such tunability proliferates their performance in various applications. Herein, we discuss the formation, multiscale structure, properties, and their modulation for the aforementioned superstructures formed from LC phases. Focusing further on ISAsomes we present Pickering emulsions stabilized by using various nanoparticles, including synthetic clay Laponite and silica nanoparticles.

The transfer of hydrophobic components among several differently nanostructured ISAsomes was studied by time-resolved X-ray scattering; the effects of Isasome-forming components are also illustrated. The continuous aqueous region of ISAsome dispersions can be loaded with water-soluble polymers that form thermoreversible hydrogels. This enables the entrapment of ISAsome systems into such hydrogel networks. Subsequent drying of these loaded systems facilitates immobilization of ISAsomes, which can be easily restored by rehydration of the loaded dry films. The formation of hydrogels in the aqueous reservoirs of W/O-nanostructured emulsions also proved advantageous in terms of tuning their viscosity and, in some cases, enhancing their stability. The current contribution covers systems with diverse structural hierarchy, ranging from equilibrium liquid crystalline nanostructures to the systems with multiple orders of length scales in their structure.