Order in a simple colloidal mixture suspension

Abstract

Preliminary SANS (small angle neutron scattering) measurements from a well characterized binary colloidal suspension of 91 nm polystyrene latex and 54 nm silica particles in water are reported for the Q range 0.02< Q (nm −1)<0.12, where Q is the scattering wave vector. The polystyrene-to-silica number ratio was 1.7 to 1 and the mixture volume fraction φ=0.15. Key measurements were the scattered intensity of the mixture, and the partial scattered intensities of the polystyrene and silica in the mixture. The partial scattered intensity of one species was obtained by contrast matching the other species in the appropriate mixture of H 2O and D 2O. Partial structure factors and pair distribution functions are compared with computer simulation data for a soft sphere mixture and with the haro sphere expressions of Aschroft and Langreth.