Controlling liquid crystal alignment using photocleavable cyanobiphenyl self-assembled monolayers

ACS Appl Mater Interfaces. 2010 Dec;2(12):3686-92. doi: 10.1021/am100832p. Epub 2010 Nov 11.

Abstract

We report on the development of novel cyano-biphenyl-based thiolate self-assembled monolayers designed to promote homeotropic alignment of calamitic liquid crystals. The molecules developed contain an ortho-nitrobenzyl protected carboxylic acid group that on irradiation by soft UV (365 nm) is cleaved to yield carboxylic acid groups exposed at the surface that promote planar alignment. Using a combination of wetting, X-ray photoelectron spectroscopy, Fourier transform-infrared reflection absorption spectroscopy, and ellipsometry we show that high photolysis yields (>90%) can be achieved and that the patterned SAMs are suitable for the controlled alignment of calamitic liquid crystals. This study further shows that such photo-patterned SAMs can be used to control the formation of focal conic domains (FCDs) in the smectic-A phase in terms of positioning and size confinement on surfaces.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Biphenyl Compounds / chemical synthesis*
  • Biphenyl Compounds / radiation effects*
  • Crystallization / methods*
  • Light
  • Liquid Crystals / chemistry*
  • Liquid Crystals / radiation effects*
  • Macromolecular Substances / chemistry
  • Materials Testing
  • Molecular Conformation
  • Surface Properties

Substances

  • Biphenyl Compounds
  • Macromolecular Substances