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Title: Studies on Langmuir Blodgett Thin Films
Authors: Dhir, Gitanjali
Supervisor: Raina, K. K.
Keywords: Langmuir-Blodgett;Liquid Crystal;Vertical alignment;Optical microscopy
Issue Date: 5-Aug-2011
Abstract: The homeotropic alignment of the nematic liquid crystal M15 on Langmuir-Blodgett monolayers of stearic acid (COOHC17H35) was studied. The Langmuir monolayers were characterized by the most basic graph known as surface pressure-area isotherm. The Langmuir monolayer of stearic acid shows a hysteresis curve. Also the Langmuir monolayers of stearic and nematic liquid crystal with different concentrations (75:25, 50:50) were formed. The surface pressure-area isotherm shows that there is an effective lift-off in the area as a function of the amount of nematic liquid crystal added to the system. The monolayer deposited on the substrate was characterized by Fourier transform of infra-red radiation (FTIR) and Scanning Electron Microscope (SEM). The monolayers of stearic acid were deposited onto glass plates coated with indium tin oxide, which were used to assemble sandwich cells of thickness that were filled with the nematic liquid crystal by the capillary action and thickness (4 micron) is controlled by using Myler spacer. The homeotropic alignment of nematic liquid crystal and film morphology was investigated as function of temperature and voltage by using optical microscopy. The result shows that the desired homeotropic alignment by the stearic acid monolayer has been provided to the nematic liquid crystal which is confirmed by the appearance of the black portion in the texture. This shows that the molecules are aligned vertically to the surface of the substrate.
Description: M.Sc. (SPMS)
Appears in Collections:Masters Theses@SPMS

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