Field-Induced Structural Transitions in Liquid Crystal Microemulsions

초록

Liquid crystal (LC) droplets have fascinating properties, such as anisotropic properties, in response to external stimuli. As LC droplet size may determine the proper application of soft composites, various results from numerical simulations and experimental observations of LC droplets are reported. Here, detailed topological responses of individual bipolar droplets to electric fields, are shown. The integration of each response influences the entire electro-optic behavior. Monodispersed LC bipolar droplets are fabricated in a polyvinyl alcohol-dissolved aqueous solution via a membrane-emulsification method. The planar anchoring, provided by the polyvinyl alcohol surface, and surface elasticity, guide the entire LC director configuration, associated with topological defects, in the droplets. By simply blade-coating the solution, bipolar axes of the droplets can be randomly placed on a flat substrate. Two different subsequential stages are found when applying voltages: 1) director reorientation, which is threshold-less and 2) topological defect movement, which exhibits a threshold-like behavior. Various initial directions of the bipolar axes with respect to the field direction provide the transition voltage between these two stages. It is believed that this study can provide important clues to handle several fundamental issues in electro-optics of encapsulated LCs, such as the determination of response times, threshold, and operating voltages.

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