The shapes of domains in two-phase monolayer systems

The kinetics of phase transitions in two dimensions can be examined experim entally in monolayers at the air/water interface. Some investigations of tr ansitions between isotropic monolayer phases have been already carried out. But many of the phases in monolayers of simple amphiphiles are mesophases in which there are textures that are related to the molecular order, much t he same as the textures in liquid crystals, and this structure will affect the morphology of evolving phases. The shapes of domains of mesoscopically ordered phases surrounded by an isotropic phase represent a balance between electrostatic fortes, the order parameters: that control the texture and t he boundary conditions at the edge of the domain. Bubbles of an isotropic p hase surrounded by an ordered phase also reflect this competition. The text ure and shape are closely coupled and there is a marked dependence on domai n or bubble size. Measurements of the shapes of bubbles and domains by Brew ster-angle microscopy and by scanning force microscopy on films transferred to solid substrates are described and compared with a recent continuum ela stic model.