Stimuli responsive microgel stabilized liquid crystal in water emulsions and their response towards chemical and biological analytes

Abstract

This dissertation conducts a comprehensive investigation on the behavior of microgel particles as Pickering emulsifiers for Liquid Crystal (LC)-in-water emulsions, a new generation droplet-based optical sensor. It investigates the impact of interfacial adsorption of microgels on the physical and sensing properties of LC droplets with the aim of establishing microgels as a viable alternative to traditional emulsifiers for LC-in-water emulsions. Synthetic polymer- and biopolymer-based microgels were prepared by free-radical precipitation polymerization and a top-down approach, respectively, and subjected to characterization using various modern experimental techniques. Microgel-stabilized LC-in-water emulsions were prepared via homogenization or the microfluidic method, and thoroughly characterized to explore the fundamental aspects of the interfacial properties of the as-obtained Pickering LC emulsions. The internal configuration of the LC within the Pickering LC droplets was analysed using a Polarized optical microscope. An extensive investigation was conducted, focusing on the physical characteristics and responsiveness of the assembly to a range of model analytes in order to establish the effectiveness of the microgels to act as emulsifiers. A detailed comparison was made to demonstrate the superiority of the microgels over classical emulsifiers (polymers) for LC-in-water emulsions. The potential of the prepared Pickering LC emulsions in practical applications such as the detection of Bile Acids and proteins was thoroughly investigated. The results concluded that microgels serve as highly efficient Pickering stabilizers for LC-in-water emulsions, paving the way for a novel category of simple, rapid, label-free, reliable, durable and economical Pickering LC emulsion-based optical sensors. newline