MULTILAYER FORMATION IN THIN-FILMS OF THERMOTROPIC LIQUID-CRYSTALS AT THE AIR-WATER-INTERFACE

Molecules that form thermotropic liquid crystals can form well-ordered thin films when spread at the air-water interface. This ordering is due to their high dipole moment and rodlike structure. We report a high degree of order compared to other monolayer systems in thin films of 4'-octyl[1,1'-biphenyl]-4-carbonitrile (8CB) spread at the air-water interface by correlating isotherm measurements and observations by Brewster angle microscopy. A first-order phase transition from a monolayer to a trilayer is shown to occur, during which circular domains are formed consisting of an interdigitated bilayer on top of the monolayer. The trilayer collapses to dense homogeneous domains, which are interpreted as stacked interdigitated bilayers with a structure similar to that of the smectic layers formed in bulk nematic 8CB near the surface. Dynamical phenomena during coalescence of domains with a different number of layers are described which may have analogs in other multilayered systems.