Azimuthal anchoring transition of nematic liquid crystals on self-assembled monolayers formed from odd and even alkanethiols

Abstract

A first order orientational transition, characterized by a 90° azimuthal rotation of the surface easy direction, is reported for nematic liquid crystals (NLCs) anchored on self-assembled monolayers (SAMs). The SAMs are formed from alkanethiols [$\mathrm{C}{\mathrm{H}}_3{\left(\mathrm{C}{\mathrm{H}}_2\right)}_{n-1\mathrm{}}\mathrm{SH};5\mathrm{}<~n<~16$] on obliquely deposited films of gold. The anchoring of the NLC is uniform and planar; the azimuthal orientation of the nematic director is, however, perpendicular to the direction of deposition of gold on SAMs formed from alkanethiols with odd chain lengths ($n=\mathrm{odd}$) and is parallel to the direction of deposition of gold on SAMs formed from alkanethiols with even ($n=\mathrm{even}$) chain lengths.