Effects of confinement and interfacial chemistry on the ordering of liquid crystals

The impact of liquid crystals (LCs) on modern technology has been profound, but until recently the technological revolution brought by LCs has been largely focused on information displays. Recently, it has been recognized that the highly cooperative and long-range ordering transitions that propagate from the interfaces of LC materials can form the basis of methods to amplify and transduce molecular interactions, enabling principles for LC-amplified chemical sensing. Although several past studies have advanced these principles, the fundamental nature of the coupling that occurs between the ordering of the LCs and the organization of the interfacial molecular assemblies remains incompletely understood. In particular, the effects of confinement on the ordering of LCs, which reflects a subtle competition between bulk and surface energetics, has not been fully elucidated. In this thesis, these issues are addressed by novel experimental designs and complementary analysis.;Firstly, this thesis describes studies of the lateral organization of phospholipids and surfactants spontaneously assembled at the aqueous-LC interface from aqueous solution. These studies have revealed the role that LCs can play in directing the organization of the interfacial molecular assemblies. Experimental observations interpreted within the framework of a simple thermodynamics model have led to identification of a new mechanism of phase separation of adsorbed molecular species that is induced by the elasticity of LCs.;Secondly, the research described in this thesis describes the development of a novel experimental technique to synthesize oil-in-water emulsions that allow precise and independent control over emulsion size and interfacial chemistry. Studies based on this experimental technique have unmasked the first definitive understanding of size-dependent changes in the molecular ordering of LCs within droplets, as well as ordering transitions within LC droplets driven by interfacial events. These fundamental advances are used to demonstrate new principles based on LC emulsions for reporting interfacial enzymatic reactions. All these above-described observations, when combined, suggest that interfaces formed between LCs and aqueous phases represent a fundamentally interesting and technologically promising class of interfaces for chemical and biological sensing, active control of interfacial assemblies and realization of stimuli-responsive materials.