Ordering Transitions at the Liquid Crystal-aqueous Interface

Download or read book Ordering Transitions at the Liquid Crystal-aqueous Interface written by and published by . This book was released on 2014 with total page 257 pages. Available in PDF, EPUB and Kindle. Book excerpt: The research described in this thesis aims to understand fundamental phenomena influencing the ordering of liquid crystals (LCs) at aqueous interfaces. While past studies have advanced the understanding of LC-solid interfaces for the development of display technology, current efforts to better understand the LC-aqueous interface are motivated in part by a desire to design stimuli-responsive materials utilizing unique properties of the LC phase. The research reported herein is organized into two parts. The first section is comprised of two studies on the effects of simple ions on the ordering of thermotropic LCs at the aqueous interface. The first study describes anchoring transitions induced by changes in pH and the addition of simple electrolytes (NaCl) to the aqueous phase, which led to the formation of an electrical double layer on the LC-side of the aqueous interface. The second study reports on the influence of specific anions of sodium salts that triggered rapid ordering transitions at neutral pH in a manner that follows a Hofmeister series of anions. Together, these investigations reveal that simple ions can have significant effects on the anchoring of LCs at the aqueous interface and suggest new insights and design principles for control over the anchoring at this interface. The second part of this thesis relates two studies of micrometer-sized droplets of thermotropic LCs "caged" within covalently assembled polymeric capsules. Orientational ordering transitions within these capsules may be coupled to wetting transitions of the LC droplet on the inside wall of the partially filled capsules in response to the presence of surfactants. The second study demonstrates that these "caged" droplets can act as sensors that are "worn" by cells, detecting the local concentration of analytes in the cellular environment. This novel approach provides a platform that can be modified to improve the design of LC droplet-based sensors. Overall, these studies reveal fundamental phenomena influencing the ordering of thermotropic LCs at the aqueous interface and provide guidance for design principles of LC-based stimuli-responsive materials and sensors.