UNIFORM ANCHORING OF NEMATIC LIQUID-CRYSTALS ON SELF-ASSEMBLED MONOLAYERS FORMED FROM ALKANETHIOLS ON OBLIQUELY DEPOSITED FILMS OF GOLD

This paper demonstrates that self-assembled monolayers (SAMs) formed b y 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 o ver centimeter-scales. In contrast, SAMs prepared on films of gold dep osited with no preferred direction cause nematic phases to form 10-100 mu m scale domains with optical axes having random azimuthal orientat ions. Self-assembled monolayers prepared from either CH3(CH2)(15)SH or CH3(CH2)(9)SH on films of gold deposited obliquely induce near-planar and azimuthally uniform anchoring of nematic phases of 4-cyano-4'-pen tylbiphenyl (5CB). Mixed SAMs formed by coadsorption of CH3(CH2)(15)SH and CH3(CH2)(9)SH cause homeotropic anchoring of nematic phases of 5C B on films of gold deposited without a preferred direction and produce a small tilt (3-5 degrees) from the normal on gold deposited obliquel y onto glass substrates. The contact angles (advancing and receding) o f hexadecane are indistinguishable when measured on SAMs supported on gold with and without a preferred direction. Liquid crystals can be us ed to detect anisotropy in these surfaces that cannot be measured by t he wetting of simple fluids such as hexadecane.