Particle diffusion in concentrated dispersions

Abstract

Three dynamic light scattering experiments on concentrated non-aqueous dispersions of spherical particles are discussed. The first two consist of measurements of the diffusion of tracer particles in different systems. In each case, host dispersions were rendered transparent by adjusting the refractive index of the dispersion medium to be the same as that of the particles. Trace amounts of particles of different refractive index, but of similar size and sterically stabilized by the same polymeric layer as the host particles, were added to the host dispersion. Thus the tracer particles provided the dominant incoherent light scattering. The measured correlation functions were analysed to provide particle mean-square displacements from which short- and long-time self-diffusion coefficients were obtained. In the third experiment the coherent scattering from concentrated dispersions of a single particle species was studied up to very high concentrations. Clear evidence of the glass transition, recently predicted, was found.