ORDERING IN 2 DIMENSIONS - OPTICAL TEXTURES IN MONOLAYERS

Optical studies of Langmuir monolayers of simple amphiphiles such as f atty acids and esters by polarized fluorescence microscopy and Brewste r-angle microscopy reveal a large variety of textures including stripe s, stars, and spirals that closely resemble textures observed in liqui d crystals. The textures represent large-scale (> 10 mu m) spontaneous organization of the molecular tilt azimuth. Phase transitions within the monolayer can be directly observed by marked changes in texture, r evealing a complex phase diagram. Many of the textures can be explaine d by a Landau-deGennes theory of tilted hexatic phases that takes into account the broken-symmetry characteristic of amphiphiles at an inter face.