ELECTROKINETIC PROPERTIES OF AQUEOUS SUSPENSIONS OF POLYSTYRENE SPHERES IN THE GAS AND LIQUID-LIKE PHASE

Previous results on the electrophoretic mobility of aqueous suspensions of polystyrene latices at low ionic strengths are controversial. We have reexamined and extended mobility measurements as a function of polyion concentration down to salt concentrations smaller than nS = 10-6 M, where the polyions are liquid-like ordered due to screened Coulomb forces. A significant increase in mobility is found below nS ∼ 10-4 M. To discuss mobilities as a function of small ion concentration, for the first time electrophoretic mobility and electric conductivity data are combined to estimate salt content. Static light scattering is used to support the latter results and to characterize the structure of the suspensions. The weak polyion concentration dependence and the increase in mobility are discussed in the light of recently published calculations. © 1991.