Quantitative studies are described of striped textures in Langmuir mon
olayers of tetradecanoic and pentadecanoic acids. The textures, which
are the result of modulations of the tilt azimuths of the molecules, h
ave been visualized with polarized fluorescence microscopy. The stripe
widths change with pressure and temperature. When the monolayer is co
mpressed beyond a threshold pressure, the stripes become unstable and
form a zig-zag pattern, which is likely the result of a crossover betw
een the bend and splay elastic constants in the monolayer.