https://doi.org/10.1007/s100510050687
Anchoring transitions with polar and non-polar nematic liquid crystals on incompletely oxidized silane substrates
Institut de Physique et
Chimie des Matériaux de Strasbourg,
Groupe des Matériaux Organiques,
23 rue du Lœss, 67037 Strasbourg, France
Received:
18
May
1998
Published online: 15 March 1999
The active oxygen gas arising from a plasma reactor is used to realize progressive chemical modifications onto silane coatings that could be particularly interesting as alignment layers for liquid crystal display applications. Depending on the oxygen density grafted onto the substrate, these alignment layers provide different zenithal anchoring angles, or pretilt angles, with anchoring transitions, for polar and non-polar nematic liquid crystals as 5CB and MBBA, respectively. The anchoring transitions are found to be smoother with the polar nematics. Such a behavior is discussed in terms of the differential wetting model by adding a cosine term to the interaction energy between the nematic and the substrate. A local justification is proposed for this symmetry breaking term.
PACS: 61.30.Gd – Orientational order of liquid crystals; electric and magnetic field effects on order / 64.70.Md – Transitions in liquid crystals / 68.45.-v – Solid fluid interfaces
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 1999
