Controlling liquid crystal alignment using photocleavable cyanobiphenyl self-assembled monolayers.
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.
Molecular and Nanoscale Physics, School of Physics and Astronomy, Centre for Molecular Nanoscience (CMNS), and Institute of Microwaves and Photonics, University of Leeds, Leeds LS2 9JT, United Kingdom.
Panida
P
Prompinit
Ammathnadu S
AS
Achalkumar
Jonathan P
JP
Bramble
Richard J
RJ
Bushby
Christoph
C
Wälti
Stephen D
SD
Evans
D001713:Biphenyl Compounds / Q000138:chemical synthesis* / Q000528:radiation effects*; D003460:Crystallization / Q000379:methods*; D008027:Light; D050866:Liquid Crystals / Q000737:chemistry* / Q000528:radiation effects*; D046911:Macromolecular Substances / Q000737:chemistry; D008422:Materials Testing; D008968:Molecular Conformation; D013499:Surface Properties
D001713:Biphenyl Compounds; D046911:Macromolecular Substances