STRUCTURE OF AN ANISOTROPIC 2-DIMENSIONAL SOLID IN A LANGMUIR FILM STUDIED BY ELECTRON-SCATTERING

In a Langmuir monolayer made of pure fluorescent NBD stearic acid, an ordered anisotropic phase was observed. The molecular structure of thi s solid phase was determined by electron scattering after transfer of the layer onto a solid substrate by the usual Langmuir-Blodgett techni que. The electron diffraction pattern shows sharp peaks, indicating tw o-dimensional long-range positional order. The diffraction pattern is analyzed by comparison with Fourier transforms of models of molecular arrangements. The simulations reveal that the aliphatic chains are pos itioned along parallel strips, in agreement with optical studies.