TEXTURES OF SURFACTANT MONOLAYERS

Microscopy studies of coexistence droplets of (tilted) surfactant mole cules absorbed at air-water interfaces have demonstrated that such dro plets contain a variety of textures. In this paper we describe the obs erved droplet textures using the Landau free energy for tilted hexatic surfactant films, supplemented by a boundary energy. It is shown that this free energy can naturally explain the morphology of droplet text ures with sixfold symmetry. In particular, it predicts (i) the existen ce of a continuous transition from straight to kinked domain walls and (ii) the appearance of spiral textures associated with spontaneous ch iral symmetry breaking in part of the phase diagram. We compare the pr edicted textures with recent polarized fluorescence and Brewster-angle microscopy experiments.