The polymer and salt induced aggregation of silica particles

Dynamic light scattering (DLS) was used to map the stability of an aqueous silica colloid in the presence of differing concentrations of sodium polystyrene sulphonate (PSS) and sodium chloride (NaCl). Additionally, values of PSS size with salt and PSS osmotic pressure were measured as a function of PSS concentration. Six theoretical maps based on DLVO and simple depletion theory were then constructed as a comparison to the experimental map using the measured values as well as two theoretical values of PSS size and osmotic pressure. It was found that DLVO overestimates the effect of salt screening and of the various comparisons those calculated using size and osmotic pressure derived from a PSS chain with 1 charge between 5 monomers showed the greatest similarities to the experimental work.