Pretilt Angle of a Nematic Liquid Crystal on Microgrooved Silica Surfaces Continuously Manipulated by the Surface Hydrophobicity

• Published in: Journal of physical chemistry. C Vol. 113; no. 22; pp. 9797 - 9803
• Main Authors: Chiou, Da-Ren, Chen, Li-Jen
• Format: Journal Article
• Language: English
• Published: American Chemical Society 04.06.2009
• Subjects: C: Surfaces, Interfaces, Catalysis
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/jp901767g

Liquid crystal alignment was investigated on the microgrooved silica surfaces modified by organosilanes. In this study, the microgrooved silica surfaces were fabricated by the soft embossing method followed by forming self-assembled monolayers (SAMs) of organosilanes on these microgrooved silica surfaces. The surface topography effect on the liquid crystal alignment is extensively discussed by using different microgrooved-patterned silica surfaces. The surface chemical nature effect on the liquid crystal alignment, as well as its pretilt angle, is also carefully examined by the SAM modifications to adjust the surface chemical property (hydrophobicity) under the condition of a fixed surface topography and liquid crystal type. The advancing contact angle of water is applied as an index of the surface hydrophobicity. The pretilt angle of the liquid crystal is successfully adjusted over the whole range from 0° to 90° continuously by simply tuning the surface hydrophobicity. The pretilt angle of the liquid crystal monotonically increases along with an increase in the advancing contact angle of water. That is, the pretilt angle of the liquid crystal is indeed only subject to the surface hydrophobicity under the condition of a fixed surface topography and liquid crystal type.