DEFECTS AND MOLECULAR ALIGNMENT IN MONOLAYERS OF THERMOTROPIC LIQUID-CRYSTALS ON WATER

Using Brewster angle microscopy, smectic disclination defects were observed in monolayers of 4'-alkyl [1,1'-biphenyl]-4-carbonitriles (nCB, n = 9, 10) at the air-water interface. Bilayer domains formed on top of the monolayer during collapse induce a splay orientation of the molecules in the surrounding monolayer along their boundary lines. In addition, bend defects are formed when the continuous bilayer breaks up to form a two-dimensional foam on the monolayer. This is the first observation of molecular alignment in monolayers on water along surface structures out of the plane of the monolayer. The results are significant for the structure of self-assembled films and biological membranes.