STRUCTURE AND INTERACTIONS IN BLACK FILMS

Very recent experiments carried out on black films, combining the dete rmination of film structure by the use of X-ray reflectivity with the determination of forces by measurement of the applied pressure on the film, are presented. The main interest of our specific experimental ap proach compared with the usual optical methods, is the very high accur acy (ca. 1 Angstrom) that can be achieved in the determination of the real thicknesses of black films. We present disjoining pressure isothe rms of ionic and non-ionic surfactants which display 'molecular steps' , revealing the action of microscopic forces.