In Situ Homeotropic Alignment of Nematic Liquid Crystals Based on Photoisomerization of Azo-Dye, Physical Adsorption of Aggregates, and Consequent Topographical Modification



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In situ homeotropic alignment is achieved by photochromic trans- to cis-isomerization of an azo-dye doped in a nematic host. The augmented dipole moment of the cis-isomer formed under UV-irradiation expedites molecular assembly into crystalline aggregates. Subsequent deposition of the aggregates creates a roughened surface and induces an anchoring transition from the initial planar to a homeotropic alignment of the LCs.