Interfacial Light Scattering Study in Microemulsions

Thermally excited waves at the interface between two fluids contain information about the structure and tension at this interface. A surface light-scattering technique based on photon correlation spectroscopy has been developed to probe the dynamics of these interfacial waves for microemulsions. The interfacial tension (IFT) as measured by this nonperturbing technique is consistent with the values obtained by conventional methods. We have studied the temperature and salinity dependence of σ (IFT) in a three-phase microemulsion system, and found that σ ~ ϵ2±0 5, where ϵ is the reduced variable |TC − T| and |Cc− C| with Tc and Cc representing the critical values of temperature and salinity, respectively. Furthermore, the correlation length, L, in the microemulsion phase has also been measured by dynamic light scattering. In the two-phase regions it was observed that σ~L−2, in accordance with the scaling law predictions. Thus, the scaled salinity and temperature parameters influence the IFT through their effect on the correlation length in the bulk microemulsion phase.