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  Abbott Research Group - UW Chemical and Biological Engineering

Laboratory for Molecular Engineering
Department of Chemical and Biological Engineering

Ordering of Liquid Crystals on Bio/Chemically Functionalized Interfaces

Surfaces of SolidsEffect of chemical oxidation of surface-immobilized ferrocene on the orientation of 5CB and MBBA. (A) Optical textures (cross polars) of 5CB in optical cells prepared with one surface supporting an array of microcontact printed circles of a monolayer formed from CH3(CH2)15SH surrounded by a monolayer formed from Fc(CH2)11SH, and an opposing surface supporting a monolayer formed from Fc(CH2)11SH. (B) Schematic illustration of the alignment of 5CB in (A). 5CB assumes a planar orientation (parallel to surface) with no preferred azimuthal direction on both surfaces. (C) Optical textures (cross polars) of 5CB containing 20 mM BP in the same optical cell as in (A). The inset (black cross in lower right of image) shows a conoscopic image indicating homeotropic alignment of 5CB in the region where both surfaces present ferrocenium. (D) Schematic illustration of the alignment of 5CB in (C). 5CB aligns perpendicular (homeotropic) to regions presenting surface-immobilized ferrocenium, but assumes a planar orientation on the circular regions formed from CH3(CH2)15SH. (E) Optical image (cross polars) of MBBA with (left side of image) and without (right side of image) BP in an optical cell with surfaces formed from Fc(CH2)11SH. Two MBBA solutions, one pure and the other containing 20 mM BP, were injected into the optical cell from opposite sides of the cell. The curve (highlighted by two dashed red arrows) indicates the transition between two regions distinguished by fine (with BP) and coarse textures (without BP) of MBBA. (F) Schematic illustration of the alignment of MBBA in (E). The distance between the two surfaces of each optical cell was measured to be 13.1 ± 0.5 µm