Photon correlation spectroscopy of liquid interfaces. II. Monolayers of fatty acids

Abstract

For pt.I see ibid., vol.12, p.1133 (1979). The viscoelastic properties of insoluble monolayers have been investigated using, for the first time, photon correlation. Thermally excited capillary waves were studied, the frequency and damping of these waves being affected by the mechanical properties of the monolayers. The film elasticity and viscosity for myristic, pentadecanoic and arachidic acids are comparable with accepted values. The variation of film elasticity with monolayer concentration indicates the occurrence of a phase transition within the monolayer. The molecular areas at which the transitions occur at 20 degrees C are within 20% of those determined from published pi -A isotherms at 21.7 degrees C.