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The orientation of nematic liquid crystals (LC) by monolayers of suitable amphiphilic compounds on solid substrates has been studied by systematic experiments using polarizing microscopy, magnetic Freedericksz‐transition, and contact angle measurements. Orientation is influenced mainly by the following parameters: 1. temperature; 2. physical properties of the substrate surface; 3. chemical properties of the substrate surface. Molecular models describing the orientating action of amphiphilic monolayers are developed and discussed in terms of the obtained quantitative results. Changes in LC orientation with film packing density and temperature can be understood as phase transitions of the system “amphiphilic monolayer + embedded LC”.

The action of solid surfaces coated with monomolecular films of amphiphilic compounds (especially lecithins) on adjacent liquid crystal phases resulting in an uniform homeotropic orientation has been investigated. The quality of orientation was found to be effected by molecular structure of the amphiphilics as well as the liquid crystals, the packing density of the film, and the temperature. The experimental results can be understood in terms of the following model: Lecithins form brush‐like films with the hydrophobic alkyl chains pointing off the glass surface. Under suitable conditions holes of molecular dimensions exist in the films into which nematogenic molecules can penetrate. By means of elastic interaction forces between these anchored molecules and the adjacent nematic bulk the homeotropization is induced.

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