Ellipsometric study of the liquid/liquid interface in a phase-separated colloid-polymer suspension

An investigation of the interface in a phase-separated colloid-polymer susp ension with ellipsometry is presented. The coefficient of ellipticity at th e Brewster angle of light reflected at the interface between the coexisting colloid-rich and polymer-rich phase was measured along two trajectories th rough the phase diagram. Interpreting the data in terms of a diffuse interf ace model, an interfacial thickness in the order of the diameter of the col loidal particles is found.