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This paper demonstrates that self-assembled monolayers (SAMs) formed by chemisorption of alkanethiols on the surface of obliquely deposited, 10 nm-thick, films of gold are useful in studies of the anchoring of liquid crystals (LCs) on surfaces. Self-assembled monolayers supported on obliquely deposited gold permit uniform anchoring of nematic LCs over centimeter-scales. In contrast, SAMs prepared on films of gold deposited with no preferred direction cause nematic phases to form 10−100 μm scale domains with optical axes having random azimuthal orientations. Self-assembled monolayers prepared from either CH3(CH2)15SH or CH3(CH2)9SH on films of gold deposited obliquely induce near-planar and azimuthally uniform anchoring of nematic phases of 4-cyano-4'-pentylbiphenyl (5CB). Mixed SAMs formed by coadsorption of CH3(CH2)15SH and CH3(CH2)9SH cause homeotropic anchoring of nematic phases of 5CB on films of gold deposited without a preferred direction and produce a small tilt (3−5°) from the normal on gold deposited obliquely onto glass substrates. The contact angles (advancing and receding) of hexadecane are indistinguishable when measured on SAMs supported on gold with and without a preferred direction. Liquid crystals can be used to detect anisotropy in these surfaces that cannot be measured by the wetting of simple fluids such as hexadecane.
Gupta et al. (Mon,) studied this question.