On the Orientation of Liquid Crystals by Monolayers of Amphiphilic Molecules

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Abstract
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”.