Abstract

Using optical second harmonic generation, we have studied the interaction between 4′-n-octyl-4-cyanobiphenyl (8CB) liquid crystal molecular monolayers and glass substrates treated with three types of silane coupling agent: MAP, DMOAP, and OTS. On adsorption from the gaseous phase at atmospheric pressure, we measure the coverage, orientation, and binding energy of monolayers on these substrates and find that, although the bulk alignment differs from different silanes, the alignment of the monolayer is unaffected. We also find a polar layer of liquid crystal at the surface of MAP and DMOAP, unlike the dimerized layers that are found in the bulk liquid crystal. The number of binding sites on these silanes is approximately equal and less than the number of sites on clean glass. Their binding energies are also slightly below that on glass. On OTS, no polar layer formed, although a dimerized bilayer was present.

© 1988 Optical Society of America