Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals, Vol.304, 171-178, 1997
Incorporation of Thermotropic Liquid-Crystals in Phospholipid Monolayers - Necessary Condition of Homeotropic Anchoring
We have studied tile monolayer phase behavior of various mixtures of dipalmitoylphosphatidylcholine (DPPC) with 4-cyano-4’-n-pentylbiphenyl (5CB) at the air/water interface by means of Langmuir technique and Brewster angle microscopy. The phase behavior is compared with the ability of 5CB to anchor homeotropically in liquid crystal cells (LC cells) whose surfaces were covered with DPPC monolayers of various molecular area using Langmuir-Blodgett technique. In the present investigations DPPC cells orient 5CB perfectly homeotropically, if the monolayers were transferred to the display surfaces as tilted phases. In case of a transferred non-tilted phase the orientation of bulk 5CB was no more homeotropical. We show that an essential prerequisite for the. homeotropic anchoring is the in corporation of 5CB in the orienting surface monolayer and thus the formation of new phases. Our conclusions are supported by DSC and x-ray experiments on fully hydrated DPPC bulk specimens (bilayer systems) mixed in various concentrations with 5CB.
Keywords:LANGMUIR-BLODGETT-FILMS;X-RAY-DIFFRACTION;ALIGNMENT TRANSITION;ORIENTATION;SURFACES;BEHAVIOR;STATES;WATER