Small-angle neutron scattering studies on binary mixtures of polystyrene and perfluorinated particles

Small-angle neutron scattering measurements (SANS) studies have been carried out on binary mixtures of small polystyrene particles (radius 315 إ) and larger perfluorinated particles (radius 664 إ). Both types of particles were spherical, monodisperse and negatively charged in the aqueous conditions used. Electrostatic interactions between the particles in each type of dispersion were examined by determining the structure factor of the dispersions. Good agreement with the experimental data and theory were obtained with the rescaled mean-spherical-approximation-model (RMSA). An alternative approach for predicting the structure factor using an equivalent hard-sphere model also gave good agreement with the experimental data. In the case of binary mixtures, with the FEP particles contrast matched, the radial distribution function indicated extensive ordering of the polystyrene particles. In addition there was evidence, at high number ratios of small particles, of cluster formation of small particles with some rejection of these from the ordered arrangement.