Phase transition in monolayers induced by adsorbed amphiphiles

A short review is given on recent progress which we achieved in the characterization of condensed monolayer phases induced by the adsorption of amphiphilic species (surfactants, proteins). The combination of surface pressure adsorption kinetics, Brewster-angle microscopy and X-ray diffraction at grazing incidence is the highly effective experimental basis of these investigations. At the beginning, a tailored amphiphile was used to be sure that artefacts caused by highly surface active trace components were avoided. So far, a first-order phase transition has been found in adsorbed monolayers of numerous other surfactants and systems. Various types of 2D modifications have been identified. A first-order phase transition can also be induced by the coadsorption of two surfactants and by the penetration of soluble surfactants into gaseous Langmuir monolayers.