SMALL-ANGLE X-RAY-ANALYSIS OF LATEX-PARTICLES USING CONTRAST VARIATION

A study of a core-shell latex consisting of a polystyrene core and a polymethylmethacrylate (PMMA) shell by small-angle x-ray scattering is presented. Since the electron density, i.e., the contrast of both polymers, can be easily matched by addition of sucrose to the dispersing agent water, the internal structure of the particles can be studied by contrast variation. The scattering intensities obtained at different contrast are all compatible with a concentric core-shell model which exhibits a finite nonuniformity of the thickness of the shell. The present analysis furthermore reveals that the interfacial region between the polystyrene and the PMMA phase must be very small.