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UBC Theses and Dissertations

Surface anchoring of nematic liquid crystals Gleeson, James Theodore


The surface anchoring of the nematic liquid crystal 5CB aligned tangentially on two different glass substrate treatments is studied. These two treatments are obliquely evaporated SiO and buffed poly(vinyl formal) deposited from solution. The latter is believed to be a new treatment and of possible importance to the twisted nematic liquid crystal display industry. Two methods are employed to measure the strength of the surface anchoring potential. The first was originally developed by Yokoyama and van Sprang, and yields the coefficient of the Rapini-Papoular anchoring potential. The second is a new method based on the Frank-Oseen elasticity theory. It is an extension of Deuling's 1972 solution of the splay Freedericksz transition. The second yields the functional form of the anchoring potential. Both methods are based on measurements of the bulk dielectric constant and the effective refractive index of a nematic sample that has undergone a splay Freedericksz transition. The first method requires both these measurements, and the second requires one or the other; both can be employed as a verification of results. The latter method is found to be very sensitive to the value of the dielectric anisotropy; this is believed to be due to not allowing for spatial variations in the scalar order parameter.

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