INTERACTIONS IN MIXTURES OF LATEX-PARTICLES AND POLYMERS AS REVEALED BY TURBIDIMETRY

We report a turbidimetric study of the depletion forces between latex particles induced by a dissolved polyelectrolyte. The system consists of a polystyrene latex and potassium polystyrene sulfonate (PSS). Sinc e turbidimetry is practically insensitive to multiple scattering the a nalysis of the mixtures of the colloid and the dissolved polymer could be extended up to latex concentrations of 50 g/l. The amount of disso lved PSS was varied between 0.025 and 0.2 wt.%. The scattering contrib ution of the polymer can be neglected in very good approximation and t he change in scattering intensity upon addition of PSS can directly be related to the effective attraction of the latex spheres caused by th e dissolved polymer. It is demonstrated that a potential based on the volume-exclusion mechanism can describe in good approximation the osmo tic compressibility resulting from the turbidimetric analysis.