CONTROL OF THE STRUCTURE OF LANGMUIR-BLODGETT-FILMS OF A DISCOTIC LIQUID-CRYSTALLINE COMPOUND VIA THE SUBPHASE COMPOSITION AND THE ADJACENT MOLECULAR ENVIRONMENT

Changes of the molecular arrangement that can be induced by means of the LB technique in the multilayers of a disc-shaped multialkynyl amphiphile are monitored by means of small angle X-ray diffraction. Studies of the monolayers at the air-water interface reveal ''edge-on'' orientation of the discs. Specific effects of the counterions (Na+, Cd2+, Pb2+ and Ba2+) and sub-solution pH on the monolayer collapse pressure, transfer efficiency and molecular order in the multilayers are found. A correlation between the monolayer properties and the ability for formation of periodic discotic structures in the presence of divalent counterions is established. The discotic molecules retain their ''edge-on'' arrangement in the highly compressed transferred films with slight irregular interdigitation of the flexible wings and inclination to the substrate normal. The tilt and the interdigitation are reduced when the discotic monolayers are deposited in alternating LB films with barium arachidate spacer layers.